diff --git a/src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java b/src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java
index 2bf5ec2..b52fb72 100644
--- a/src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java
+++ b/src/main/java/rocks/zipcode/quiz4/collections/WordCounter.java
@@ -1,12 +1,41 @@
 package rocks.zipcode.quiz4.collections;
 
-import java.util.Map;
+import java.util.*;
 
 public class WordCounter {
+    private final String[] stringArray;
+
     public WordCounter(String... strings) {
+        this.stringArray= strings;
     }
 
     public Map<String, Integer> getWordCountMap() {
-        return null;
+        Map<String, Integer> map = new HashMap<>();
+        List<String> allWords = getAllWords();
+        for(String word : allWords) {
+            map.put(word, getNumberOfOccurrences(allWords, word));
+        }
+        return map;
+    }
+
+    private Integer getNumberOfOccurrences(List<String> allWords, String wordToCheck) {
+        int count = 0;
+        for(String word : allWords) {
+            if(word.equals(wordToCheck)) {
+                count++;
+            }
+        }
+        return count;
+    }
+
+    private List<String> getAllWords() {
+        List<String> result = new ArrayList<>();
+        for(String string : stringArray) {
+            String[] words = string.split(" ");
+            for(String word : words) {
+                result.add(word);
+            }
+        }
+        return result;
     }
 }
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..9502b69 100644
--- a/src/main/java/rocks/zipcode/quiz4/collections/culonary/Food.java
+++ b/src/main/java/rocks/zipcode/quiz4/collections/culonary/Food.java
@@ -12,7 +12,8 @@ public List<Spice> getAllSpices() {
     }
 
     public <SpiceType extends Class<? extends Spice>> Map<SpiceType, Integer> getSpiceCount() {
-        return null;
+        Map<SpiceType, Integer> spiceCount = null;
+        return spiceCount;
     }
 
     public void applySpice(Spice 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..f627101 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 +3,6 @@
 /**
  * @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..95a0a1d 100644
--- a/src/main/java/rocks/zipcode/quiz4/fundamentals/Calculator.java
+++ b/src/main/java/rocks/zipcode/quiz4/fundamentals/Calculator.java
@@ -5,15 +5,19 @@
  */
 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[] array;
+        for (int currentIndex = 0; currentIndex < value.length; currentIndex++) {
+            Double element = value[currentIndex];
+            squareRoot(element);
+        }return null;
     }
 
     public static Double[] squares(Double... values) {
@@ -21,15 +25,15 @@ public static Double[] squares(Double... 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..94d3cd4 100644
--- a/src/main/java/rocks/zipcode/quiz4/fundamentals/StringUtils.java
+++ b/src/main/java/rocks/zipcode/quiz4/fundamentals/StringUtils.java
@@ -5,15 +5,16 @@
  */
 public class StringUtils {
     public static Character getMiddleCharacter(String string) {
-        return null;
+        char middleChar = string.charAt(string.length()/2);
+        return middleChar;
     }
 
     public static String capitalizeMiddleCharacter(String str) {
-        return null;
+        return getMiddleCharacter(str).toString().toUpperCase();
     }
 
     public static String lowerCaseMiddleCharacter(String str) {
-        return null;
+        return getMiddleCharacter(str).toString().toLowerCase();
     }
 
     public static Boolean isIsogram(String str) {
@@ -21,14 +22,39 @@ public static Boolean isIsogram(String str) {
     }
 
     public static Boolean hasDuplicateConsecutiveCharacters(String str) {
-        return null;
+        char[] duplicateCharacters = str.toCharArray();
+        char previousElement;
+        for (int currentIndex = 1; currentIndex < duplicateCharacters.length; currentIndex++) {
+             char currentElement = duplicateCharacters[currentIndex];
+             previousElement = duplicateCharacters[currentIndex-1];
+             if(previousElement == currentElement){
+                 return true;
+             }
+        }
+        return false;
     }
 
     public static String removeConsecutiveDuplicateCharacters(String str) {
-        return null;
+        String result = "";
+        char[] duplicateCharacters = str.toCharArray();
+        for (int currentIndex = 0; currentIndex < duplicateCharacters.length; currentIndex++){
+            char currentElement = duplicateCharacters[currentIndex];
+            if(!hasDuplicateConsecutiveCharacters(str)){
+                result += currentElement;
+            }
+        }
+        return result;
     }
 
     public static String invertCasing(String str) {
-        return null;
-    }
+       // String result = "";
+       // Character[] invertedChar = str.toCharArray().toString().toUpperCase();
+      //  Character lowerCaseFirstChar = str.toCharArray().toString().toLowerCase();
+      //  for (int currentIndex = 0; currentIndex < invertedChar.length; currentIndex++) {
+       //     char currentElement = invertedChar[currentIndex];
+      //      if (currentElement == invertedChar[currentIndex+1]) {
+         //   }
+      //  }
+       return null;
+   }
 }
\ 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..467318b 100644
--- a/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Account.java
+++ b/src/main/java/rocks/zipcode/quiz4/objectorientation/account/Account.java
@@ -4,10 +4,13 @@
  * @author leon on 30/12/2018.
  */
 public class Account extends BankAccount {
+    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..92d0058 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 +1,26 @@
 package rocks.zipcode.quiz4.objectorientation.account;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /**
  * @author leon on 27/12/2018.
  */
 public class Bank {
+    List<BankAccount> bankAccountList = new ArrayList<>();
+
+
     public BankAccount removeBankAccountByIndex(Integer indexNumber) {
-        return null;
+        BankAccount account = bankAccountList.get(indexNumber);
+        bankAccountList.remove(account);
+        return account;
     }
 
     public void addBankAccount(BankAccount bankAccount) {
+        bankAccountList.add(bankAccount);
     }
 
     public Boolean containsBankAccount(BankAccount bankAccount) {
-        throw new UnsupportedOperationException("Method not yet implemented");
+        return bankAccountList.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..2db7478 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 +3,25 @@
 /**
  * @author leon on 27/12/2018.
  */
-public class BankAccount {
-    public void setBalance(Double val) {
+public class BankAccount implements Transactable {
+    private Double balance = 0.0;
+
+    public void setBalance(Double balance) {
+        this.balance = balance;
+    }
+
+    @Override
+    public void deposit(Double amountToIncreaseBy) {
+        setBalance(getBalance() + amountToIncreaseBy);
+    }
+
+    @Override
+    public void withdrawal(Double amountToDecreaseBy) {
+        deposit(-amountToDecreaseBy);
+    }
+
+    @Override
+    public Double getBalance() {
+        return 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..fd04440 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 +3,63 @@
 /**
  * @author leon on 30/12/2018.
  */
-public class Employee {
+public class Employee implements Transactable, Worker {
+    private BankAccount bankAccount;
+    private double numberOfHoursWorked;
+    private double hourlyWage;
+
     public Employee() {
+        this.hourlyWage = 35.0;
+        this.numberOfHoursWorked = 0.0;
+        this.bankAccount = new BankAccount();
     }
 
+
     public Employee(BankAccount bankAccount) {
+        this.bankAccount = bankAccount;
     }
 
     public BankAccount getBankAccount() {
-        return null;
+        return bankAccount;
     }
 
     public void setBankAccount(BankAccount bankAccount) {
+        this.bankAccount = bankAccount;
+    }
+
+    @Override
+    public void deposit(Double amountToIncreaseBy) {
+        bankAccount.deposit(amountToIncreaseBy);
+    }
+
+    @Override
+    public void withdrawal(Double amountToDecreaseBy) {
+        bankAccount.withdrawal(amountToDecreaseBy);
+
+    }
+
+    @Override
+    public Double getBalance() {
+        return bankAccount.getBalance();
+    }
+
+    @Override
+    public void increaseHoursWorked(Double numberOfHours) {
+        this.numberOfHoursWorked += numberOfHours;
+    }
+
+    @Override
+    public Double getHoursWorked() {
+        return this.numberOfHoursWorked;
+    }
+
+    @Override
+    public Double getHourlyWage() {
+        return hourlyWage;
+    }
 
+    @Override
+    public Double getMoneyEarned() {
+        return getHourlyWage() * numberOfHoursWorked;
     }
 }