diff --git a/src/main/java/rocks/zipcode/quiz4/arrays/ArrayUtils.java b/src/main/java/rocks/zipcode/quiz4/arrays/ArrayUtils.java
index 6deaf61..9c56e08 100644
--- a/src/main/java/rocks/zipcode/quiz4/arrays/ArrayUtils.java
+++ b/src/main/java/rocks/zipcode/quiz4/arrays/ArrayUtils.java
@@ -5,18 +5,34 @@
  */
 public class ArrayUtils {
     public static String getMiddleElement(String[] values) {
-        return null;
+        return values[values.length/2];
     }
 
     public static String[] removeMiddleElement(String[] values) {
-        return null;
+            String RM[]= new String[(values.length-1)];
+            int count=0;
+             for (int i=0; i< values.length; i++)
+                 if( i==values.length/2)
+                 {
+
+                 }
+                else{
+                    RM[count]= values[i];
+                    count++;
+                 }
+        return RM;
     }
 
     public static String getLastElement(String[] values) {
-        return null;
+        return values[values.length-1];
     }
 
     public static String[] removeLastElement(String[] values) {
-        return null;
+        String RL[] = new String[(values.length - 1)];
+        for (int i = 0; i < values.length - 1; i++)
+        {
+            RL[i] = values[i];
+    }
+        return RL;
     }
 }
\ No newline at end of file
diff --git a/src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java b/src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java
index 2bf5ec2..869fa90 100644
--- a/src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java
+++ b/src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java
@@ -1,12 +1,24 @@
 package rocks.zipcode.quiz4.collections;
 
+import java.util.HashMap;
 import java.util.Map;
 
 public class WordCounter {
+    String[] arr;
     public WordCounter(String... strings) {
+        arr= strings;
     }
 
+
     public Map<String, Integer> getWordCountMap() {
-        return null;
+        Map<String, Integer> map =new HashMap<>();
+        for(String x : arr){
+            if(map.containsKey(x)){
+                map.replace(x, map.get(x)+1);
+            }else{
+                map.put(x,1);
+            }
+        }
+        return map;
     }
 }
diff --git a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Curry.java b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Curry.java
index 199cefc..c4aeb81 100644
--- a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Curry.java
+++ b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Curry.java
@@ -1,4 +1,13 @@
 package rocks.zipcode.quiz4.collections.culonary;
 
-public class Curry {
+public class Curry implements Spice {
+    private String name;
+    public Curry(){
+        this.name= this.getClass().getSimpleName();
+    }
+
+    @Override
+    public String getName() {
+        return name;
+    }
 }
diff --git a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Food.java b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Food.java
index e06abbc..db1b9be 100644
--- a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Food.java
+++ b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Food.java
@@ -1,5 +1,7 @@
 package rocks.zipcode.quiz4.collections.culonary;
 
+import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -7,14 +9,18 @@
  * @author leon on 27/12/2018.
  */
 public class Food {
+    List<Spice> spices=new ArrayList<>();
     public List<Spice> getAllSpices() {
-        return null;
+        return this.spices;
     }
 
     public <SpiceType extends Class<? extends Spice>> Map<SpiceType, Integer> getSpiceCount() {
-        return null;
+        Map<SpiceType, Integer> spiceCount = new HashMap<>();
+        spiceCount.put((SpiceType)spices.get(0).getClass(), spices.size());
+        return spiceCount;
     }
 
     public void applySpice(Spice spice) {
+        spices.add(spice);
     }
 }
diff --git a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Ginger.java b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Ginger.java
index 3c4e177..e1d6507 100644
--- a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Ginger.java
+++ b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Ginger.java
@@ -3,5 +3,14 @@
 /**
  * @author leon on 27/12/2018.
  */
-public class Ginger {
+public class Ginger implements Spice{
+    private String name;
+    public Ginger(){
+        this.name =this.getClass().getSimpleName();
+    }
+
+    @Override
+    public String getName() {
+        return name;
+    }
 }
diff --git a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Pepper.java b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Pepper.java
index 4b771a8..6edc329 100644
--- a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Pepper.java
+++ b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Pepper.java
@@ -3,5 +3,14 @@
 /**
  * @author leon on 27/12/2018.
  */
-public class Pepper {
+public class Pepper implements Spice{
+    private String name;
+    public Pepper(){
+        this.name =this.getClass().getSimpleName();
+    }
+
+    @Override
+    public String getName() {
+        return name;
+    }
 }
diff --git a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Spice.java b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Spice.java
index 9ab865b..e73857c 100644
--- a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Spice.java
+++ b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Spice.java
@@ -4,4 +4,5 @@
  * @author leon on 27/12/2018.
  */
 public interface Spice {
+    String getName();
 }
diff --git a/src/main/java/rocks/zipcode/quiz4/fundamentals/Calculator.java b/src/main/java/rocks/zipcode/quiz4/fundamentals/Calculator.java
index 02f2618..a0417b6 100644
--- a/src/main/java/rocks/zipcode/quiz4/fundamentals/Calculator.java
+++ b/src/main/java/rocks/zipcode/quiz4/fundamentals/Calculator.java
@@ -5,31 +5,37 @@
  */
 public class Calculator {
     public static Double squareRoot(Double value) {
-        return null;
+        return Math.sqrt(value);
     }
 
     public static Double square(Double value) {
-        return null;
+        return value * value;
     }
 
     public static Double[] squareRoots(Double... value) {
-        return null;
+        Double[] result = new Double[value.length];
+        for (int i = 0; i < value.length; i++) {
+        result[i] = Math.sqrt(value[i]);
     }
-
+return result;
+}
     public static Double[] squares(Double... values) {
-        return null;
+        Double[] result = new Double[values.length];
+        for (int i = 0; i < values.length; i++) {
+            result[i] = values[i] * values[i];
+        }
+        return result;
     }
-
     public static Double add(Double value1, Double value2) {
-        return null;
+        return value1 + value2;
     }
 
     public static Double subtract(Double value1, Double value2) {
-        return null;
+        return value1 - value2;
     }
 
 
     public static Double divide(Double divisor, Double dividend) {
-        return null;
+        return divisor/dividend;
     }
 }
diff --git a/src/main/java/rocks/zipcode/quiz4/fundamentals/StringUtils.java b/src/main/java/rocks/zipcode/quiz4/fundamentals/StringUtils.java
index 5ec61be..d9b683e 100644
--- a/src/main/java/rocks/zipcode/quiz4/fundamentals/StringUtils.java
+++ b/src/main/java/rocks/zipcode/quiz4/fundamentals/StringUtils.java
@@ -1,34 +1,73 @@
 package rocks.zipcode.quiz4.fundamentals;
 
+
 /**
  * @author leon on 21/12/2018.
  */
 public class StringUtils {
     public static Character getMiddleCharacter(String string) {
-        return null;
+        return string.charAt(string.length() / 2);
     }
 
     public static String capitalizeMiddleCharacter(String str) {
-        return null;
+        return str.substring(0, str.length() / 2) +
+                getMiddleCharacter(str.toUpperCase()) + str.substring(str.length() / 2 + 1);
+
     }
 
     public static String lowerCaseMiddleCharacter(String str) {
-        return null;
+        return str.substring(0, (str.length() / 2))+
+         getMiddleCharacter(str.toLowerCase()) + str.substring(str.length() / 2+1);
     }
 
     public static Boolean isIsogram(String str) {
-        return null;
+
+        for( int i =1; i<str.length(); i++){
+            char c = str.charAt(i);
+            if(str.indexOf(c)!=i){
+                return false;
+            }
+        }
+        return true;
     }
 
+
     public static Boolean hasDuplicateConsecutiveCharacters(String str) {
-        return null;
+
+
+        for(int i =1; i<str.length();i++){
+            if(str.charAt(i)== str.charAt(i-1)){
+                  return true;
+            }
+        }
+        return false;
     }
 
+
+
+
+
     public static String removeConsecutiveDuplicateCharacters(String str) {
-        return null;
+        for(int i = 0; i< str.length()-1; i++){
+            if (str.charAt(i)==str.charAt(i+1)){
+                str= str.substring(0,i)+ str.substring(i+2);
+            }
+        }
+        return str;
     }
 
     public static String invertCasing(String str) {
-        return null;
+        char[] arr= str.toCharArray();
+        int count =0;
+        for(char x :arr){
+            if(Character.isUpperCase(x)){
+                arr[count] = Character.toLowerCase(x);
+            }
+            else{
+                arr[count] = Character.toUpperCase(x);
+            }
+            count++;
+        }
+        return new String(arr);
     }
 }
\ No newline at end of file
diff --git a/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Account.java b/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Account.java
index 40eb4a8..28093e4 100644
--- a/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Account.java
+++ b/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Account.java
@@ -3,11 +3,18 @@
 /**
  * @author leon on 30/12/2018.
  */
-public class Account extends BankAccount {
-    public Long getId() {
-        return null;
+public class Account  {
+    private Long id;
+     public Account(){}
+
+    public Account (Long id) {
+        this.id=id;
     }
 
-    public void setId(Long id) {
+    public Long getId() {
+        return this.id;
+    }
+    public void setId(Long id){
+         this.id= id;
     }
 }
diff --git a/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Bank.java b/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Bank.java
index 0dd4183..cd80576 100644
--- a/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Bank.java
+++ b/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Bank.java
@@ -1,17 +1,24 @@
 package rocks.zipcode.quiz4.objectorientation.account;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /**
  * @author leon on 27/12/2018.
  */
 public class Bank {
+    private List<BankAccount> accountList= new ArrayList<>();
     public BankAccount removeBankAccountByIndex(Integer indexNumber) {
-        return null;
+        BankAccount removed = accountList.get(indexNumber);
+        accountList.remove(removed);
+        return removed;
     }
 
     public void addBankAccount(BankAccount bankAccount) {
+        accountList.add(bankAccount);
     }
 
     public Boolean containsBankAccount(BankAccount bankAccount) {
-        throw new UnsupportedOperationException("Method not yet implemented");
+        return accountList.contains(bankAccount);
     }
 }
diff --git a/src/main/java/rocks/zipcode/quiz4/objectorientation/account/BankAccount.java b/src/main/java/rocks/zipcode/quiz4/objectorientation/account/BankAccount.java
index 70ccb74..67bea91 100644
--- a/src/main/java/rocks/zipcode/quiz4/objectorientation/account/BankAccount.java
+++ b/src/main/java/rocks/zipcode/quiz4/objectorientation/account/BankAccount.java
@@ -3,7 +3,39 @@
 /**
  * @author leon on 27/12/2018.
  */
-public class BankAccount {
-    public void setBalance(Double val) {
+public class BankAccount extends Account implements Transactable {
+    private  Double balance;
+
+    public BankAccount() {
+        this.balance= 0.0;
     }
-}
+
+
+
+    @Override
+    public void deposit(Double amountToIncreaseBy) {
+            if (amountToIncreaseBy < 0)
+                throw new IllegalArgumentException();
+                balance += amountToIncreaseBy;
+            }
+
+
+            @Override
+            public void withdrawal (Double amountToDecreaseBy){
+                if (amountToDecreaseBy < 0 || balance - amountToDecreaseBy<0) throw  new IllegalArgumentException();
+                balance -= amountToDecreaseBy;
+            }
+
+
+            @Override
+            public Double getBalance () {
+                return balance;
+            }
+            public void setBalance (Double val){
+                this.balance = val;
+
+            }
+
+
+        }
+
diff --git a/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Employee.java b/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Employee.java
index 8407f1a..30aa007 100644
--- a/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Employee.java
+++ b/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Employee.java
@@ -3,18 +3,74 @@
 /**
  * @author leon on 30/12/2018.
  */
-public class Employee {
+public class Employee extends BankAccount implements Worker, Transactable{
+
+    private BankAccount personalAccount;
+    private Double numberOfHours;
+    private Double hourlyWage;
+    private Double moneyEarned;
+
     public Employee() {
+        this(new BankAccount());
+
+
     }
 
+
     public Employee(BankAccount bankAccount) {
+        this.personalAccount = bankAccount;
+        this.hourlyWage = 35.0;
+        this.numberOfHours =0.0;
+        this.moneyEarned= 0.0;
+
     }
 
+
+
     public BankAccount getBankAccount() {
-        return null;
+
+        return personalAccount;
     }
 
     public void setBankAccount(BankAccount bankAccount) {
+        this.personalAccount= bankAccount;
+
+    }
+
+    @Override
+    public void deposit(Double amountToIncreaseBy) {
+        personalAccount.deposit(amountToIncreaseBy);
+    }
 
+    @Override
+    public void withdrawal(Double amountToDecreaseBy) {
+        personalAccount.withdrawal(amountToDecreaseBy);
+    }
+
+    @Override
+    public Double getBalance() {
+        return personalAccount.getBalance();
+    }
+
+    @Override
+    public void increaseHoursWorked(Double numberOfHours) {
+        this.numberOfHours += numberOfHours;
+    }
+
+    @Override
+    public Double getHoursWorked() {
+        return numberOfHours;
+    }
+
+    @Override
+    public Double getHourlyWage() {
+        return hourlyWage;
+    }
+
+    @Override
+    public Double getMoneyEarned() {
+        return moneyEarned;
     }
 }
+
+
diff --git a/src/test/java/rocks/zipcode/quiz4/objectorientation/bankaccount/WithdrawalPositiveTest.java b/src/test/java/rocks/zipcode/quiz4/objectorientation/bankaccount/WithdrawalPositiveTest.java
index b72a6b2..83854f3 100644
--- a/src/test/java/rocks/zipcode/quiz4/objectorientation/bankaccount/WithdrawalPositiveTest.java
+++ b/src/test/java/rocks/zipcode/quiz4/objectorientation/bankaccount/WithdrawalPositiveTest.java
@@ -50,4 +50,4 @@ public void test(Double initialBalance, Double withdrawalAmount) {
         // then
         Assert.assertEquals(expected, actual);
     }
-}
+}
\ No newline at end of file