diff --git a/src/main/java/rocks/zipcode/quiz4/arrays/ArrayUtils.java b/src/main/java/rocks/zipcode/quiz4/arrays/ArrayUtils.java
index 6deaf61..aad96e9 100644
--- a/src/main/java/rocks/zipcode/quiz4/arrays/ArrayUtils.java
+++ b/src/main/java/rocks/zipcode/quiz4/arrays/ArrayUtils.java
@@ -5,18 +5,29 @@
  */
 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[] newArray = new String[values.length - 1];
+        for (int i = 0; i < values.length / 2; i++) {
+            newArray[i] = values[i];
+        }
+        for (int i = (values.length/2); i < newArray.length; i++) {
+            newArray[i] = values[i+1];
+        }
+        return newArray;
     }
 
     public static String getLastElement(String[] values) {
-        return null;
+        return values[values.length - 1];
     }
 
     public static String[] removeLastElement(String[] values) {
-        return null;
+        String[] newArray = new String[values.length - 1];
+        for (int i = 0; i < newArray.length; i++) {
+            newArray[i] = values[i];
+        }
+        return newArray;
     }
 }
\ 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..99320e4 100644
--- a/src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java
+++ b/src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java
@@ -1,12 +1,26 @@
 package rocks.zipcode.quiz4.collections;
 
+import java.util.HashMap;
 import java.util.Map;
 
 public class WordCounter {
+    String[]strings;
+
     public WordCounter(String... strings) {
+        this.strings=strings;
     }
 
     public Map<String, Integer> getWordCountMap() {
-        return null;
+        Map<String,Integer>wordCount=new HashMap<>();
+        for (String word:strings){
+
+            if (!wordCount.containsKey(word)) {
+                wordCount.put(word, 1);
+            } else {
+                wordCount.put(word, wordCount.get(word) + 1);
+            }
+
+        }
+        return wordCount;
     }
 }
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..c6b96b4 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 +1,4 @@
 package rocks.zipcode.quiz4.collections.culonary;
 
-public class Curry {
+public class Curry implements Spice {
 }
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..cece18a 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 +1,9 @@
 package rocks.zipcode.quiz4.collections.culonary;
 
+import com.sun.codemodel.internal.JForEach;
+
+import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -7,14 +11,33 @@
  * @author leon on 27/12/2018.
  */
 public class Food {
+    List<Spice>spiceList;
+
+    public Food(){
+        this.spiceList = new ArrayList<Spice>();
+    }
+
     public List<Spice> getAllSpices() {
-        return null;
+        return this.spiceList;
     }
 
     public <SpiceType extends Class<? extends Spice>> Map<SpiceType, Integer> getSpiceCount() {
-        return null;
+            Map<SpiceType,Integer> spiceCount = new HashMap<>();
+        for (Spice s: spiceList) {
+            SpiceType spicy = (SpiceType)s.getClass();
+            if (!spiceCount.containsKey(spicy)) {
+                spiceCount.put(spicy, 1);
+            } else {
+                spiceCount.put(spicy, spiceCount.get(spicy) + 1);
+            }
+
+        }
+        return spiceCount;
     }
 
+
+
     public void applySpice(Spice spice) {
+        spiceList.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..1667d46 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 +3,5 @@
 /**
  * @author leon on 27/12/2018.
  */
-public class Ginger {
+public class Ginger implements Spice {
 }
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..eafd2a5 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 +3,5 @@
 /**
  * @author leon on 27/12/2018.
  */
-public class Pepper {
+public class Pepper implements Spice {
 }
diff --git a/src/main/java/rocks/zipcode/quiz4/fundamentals/Calculator.java b/src/main/java/rocks/zipcode/quiz4/fundamentals/Calculator.java
index 02f2618..629b0d7 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;
+        for (int i = 0; i < value.length; i++) {
+            value[i]=Math.sqrt(value[i]);
+        }
+        return value;
     }
 
     public static Double[] squares(Double... values) {
-        return null;
+        for (int i = 0; i < values.length; i++) {
+            values[i]=values[i]*values[i];
+        }
+        return values;
     }
 
     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..45b68cd 100644
--- a/src/main/java/rocks/zipcode/quiz4/fundamentals/StringUtils.java
+++ b/src/main/java/rocks/zipcode/quiz4/fundamentals/StringUtils.java
@@ -1,34 +1,79 @@
 package rocks.zipcode.quiz4.fundamentals;
 
+import java.util.Arrays;
+
 /**
  * @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;
+        String newStr = "";
+        int index = str.length() / 2;
+        newStr += str.substring(0, index);
+        newStr += Character.toUpperCase(str.charAt(index));
+        newStr += str.substring(index + 1);
+        return newStr;
     }
 
     public static String lowerCaseMiddleCharacter(String str) {
-        return null;
+        String newStr = "";
+        int index = str.length() / 2;
+        newStr += str.substring(0, index);
+        newStr += Character.toLowerCase(str.charAt(index));
+        newStr += str.substring(index + 1);
+        return newStr;
     }
 
     public static Boolean isIsogram(String str) {
-        return null;
+        String string = str.toLowerCase();
+        char arr[] = str.toCharArray();
+
+        Arrays.sort(arr);
+        for (int i = 0; i < string.length() - 1; i++) {
+            if (arr[i] == arr[i + 1])
+                return false;
+        }
+        return true;
     }
 
+
     public static Boolean hasDuplicateConsecutiveCharacters(String str) {
-        return null;
+        for (int i = 0; i < str.length() - 1; i++) {
+            if (str.charAt(i) == str.charAt(i + 1)) {
+                return true;
+            }
+        }
+        return false;
     }
 
     public static String removeConsecutiveDuplicateCharacters(String str) {
-        return null;
+        String string = "";
+
+        for (int i = 0; i < str.length()-1; i++) {
+            if (str.charAt(i) == str.charAt(i + 1)) {
+                i=i+2;
+            }
+            string += str.charAt(i);
+        }
+        return string;
     }
 
     public static String invertCasing(String str) {
-        return null;
+        String string = "";
+        for (int i = 0; i < str.length(); i++) {
+            if (Character.isUpperCase(str.charAt(i))) {
+                string += Character.toLowerCase(str.charAt(i));
+            } else if (Character.isLowerCase(str.charAt(i))) {
+                string += Character.toUpperCase(str.charAt(i));
+            }else{
+            string+=str.charAt(i);
+
+        }
+
     }
-}
\ No newline at end of file
+        return string;
+}}
\ 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..2c0b88f 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 +3,13 @@
 /**
  * @author leon on 30/12/2018.
  */
-public class Account extends BankAccount {
+public class Account {
+    private Long id;
     public Long getId() {
-        return null;
+        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..4fecc15 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 +1,30 @@
 package rocks.zipcode.quiz4.objectorientation.account;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /**
  * @author leon on 27/12/2018.
  */
 public class Bank {
+    ArrayList<BankAccount> accounts;
+
+    public Bank(){
+        this.accounts = new ArrayList<>();
+    }
+
+
+
     public BankAccount removeBankAccountByIndex(Integer indexNumber) {
+        this.accounts.remove(indexNumber);
         return null;
     }
-
     public void addBankAccount(BankAccount bankAccount) {
+        this.accounts.add(bankAccount);
     }
 
     public Boolean containsBankAccount(BankAccount bankAccount) {
-        throw new UnsupportedOperationException("Method not yet implemented");
+        return this.accounts.contains(bankAccount);
+      //  throw new UnsupportedOperationException("Method not yet implemented");
     }
 }
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..38502d8 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 +3,37 @@
 /**
  * @author leon on 27/12/2018.
  */
-public class BankAccount {
+public class BankAccount extends Account implements Transactable {
+    private Double balance;
+
+
+    public BankAccount(){
+        this.balance=0.0;
+    }
     public void setBalance(Double val) {
+        this.balance = val;
+    }
+
+    @Override
+    public void deposit(Double amountToIncreaseBy) throws IllegalArgumentException {
+        if (amountToIncreaseBy < 0) {
+            throw new IllegalArgumentException();
+        }
+        balance += amountToIncreaseBy;
+
+    }
+
+    @Override
+    public void withdrawal(Double amountToDecreaseBy) throws IllegalArgumentException {
+        if (balance < amountToDecreaseBy || amountToDecreaseBy < 0) {
+            throw new IllegalArgumentException();
+        }
+        balance -= amountToDecreaseBy;
+    }
+
+
+    @Override
+    public Double getBalance() {
+        return this.balance;
     }
 }
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..a701754 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 +3,71 @@
 /**
  * @author leon on 30/12/2018.
  */
-public class Employee {
+public class Employee implements Worker, Transactable {
+    BankAccount bankAccount;
+    Double hourlyWage;
+    Double hoursWorked;
+
+
     public Employee() {
+        this.bankAccount = new BankAccount();
+        this.hourlyWage = 35.0;
+        this.hoursWorked = 0.0;
     }
 
     public Employee(BankAccount bankAccount) {
+        this.bankAccount = bankAccount;
+        this.hourlyWage=35.0;
+        this.hoursWorked=0.0;
+    }
+
+    public Employee(BankAccount bankAccount, Double hourlyWage, Double hoursWorked) {
+        this.bankAccount = bankAccount;
+        this.hourlyWage = hourlyWage;
+        this.hoursWorked = hoursWorked;
     }
 
     public BankAccount getBankAccount() {
-        return null;
+        return this.bankAccount;
     }
 
     public void setBankAccount(BankAccount bankAccount) {
+        this.bankAccount = bankAccount;
+    }
+
+    @Override
+    public void deposit(Double amountToIncreaseBy) {
+        this.bankAccount.deposit(amountToIncreaseBy);
+
+    }
+
+    @Override
+    public void withdrawal(Double amountToDecreaseBy) {
+        this.bankAccount.withdrawal(amountToDecreaseBy);
+    }
+
+    @Override
+    public Double getBalance() {
+        return this.bankAccount.getBalance();
+    }
+
+    @Override
+    public void increaseHoursWorked(Double numberOfHours) {
+        this.hoursWorked+=numberOfHours;
+    }
+
+    @Override
+    public Double getHoursWorked() {
+        return this.hoursWorked;
+    }
+
+    @Override
+    public Double getHourlyWage() {
+        return this.hourlyWage;
+    }
 
+    @Override
+    public Double getMoneyEarned() {
+        return this.hourlyWage * this.hoursWorked;
     }
 }