diff --git a/assignment4/Question1/StartGrading.java b/assignment4/Question1/StartGrading.java
new file mode 100644
index 0000000..c05a912
--- /dev/null
+++ b/assignment4/Question1/StartGrading.java
@@ -0,0 +1,12 @@
+public class StartGrading {	
+	public static void testCourse() 
+	{ 
+		//  Since we cannot create any Course object,
+		//the testCourse method of the Course class must be empty. 
+	} 
+  
+	public static void main(String[] args)  
+	{ 
+		testCourse(); 
+	} 
+}
diff --git a/assignment4/Question2/StartGrading.java b/assignment4/Question2/StartGrading.java
new file mode 100644
index 0000000..086a1a3
--- /dev/null
+++ b/assignment4/Question2/StartGrading.java
@@ -0,0 +1,17 @@
+public class StartGrading {	
+	public static void testCourse() 
+	{ 
+		//  Since we cannot create any Course object,
+		//the testCourse method of the Course class must be empty. 
+	} 
+	public static void testMajorRequired()  
+	{   
+		//Since we cannot create any MajorRequired object,  
+		//the testMajorRequired method of the Course class must be empty. 
+    } 
+	public static void main(String[] args)  
+	{     
+		testCourse(); 
+		testMajorRequired(); 
+	} 
+}
diff --git a/assignment4/Question3/StartGrading.java b/assignment4/Question3/StartGrading.java
new file mode 100644
index 0000000..3f767e2
--- /dev/null
+++ b/assignment4/Question3/StartGrading.java
@@ -0,0 +1,26 @@
+public class StartGrading {	
+	public static void testCourse() 
+	{ 
+		//  Since we cannot create any Course object, 
+		//the testCourse method of the Course class must be empty. 
+	}
+	
+	public static void testMajorRequired()  
+	{ 
+		//Since we cannot create any MajorRequired object,  
+		//the testMajorRequired method of the Course class must be empty. 
+    } 
+
+	public static void testMajorElective()  
+	{ 
+		//Since we cannot create any MajorElective object, 
+		//the testMajorElective method of the Course class must be empty. 
+	} 
+
+	public static void main(String[] args)  
+	{ 
+		testCourse(); 
+		testMajorElective(); 
+		testMajorRequired(); 
+	} 
+}
diff --git a/assignment4/Question4/StartGrading.java b/assignment4/Question4/StartGrading.java
new file mode 100644
index 0000000..776a47a
--- /dev/null
+++ b/assignment4/Question4/StartGrading.java
@@ -0,0 +1,38 @@
+public class StartGrading {	
+	public static void testCourse() 
+	{ 
+		//  Since we cannot create any Course object, 
+		//the testCourse method of the Course class must be empty. 
+	}
+	
+	public static void testMajorRequired()  
+	{ 
+		//Since we cannot create any MajorRequired object,  
+		//the testMajorRequired method of the Course class must be empty. 
+    } 
+
+	public static void testMajorElective()  
+	{ 
+		//Since we cannot create any MajorElective object, 
+		//the testMajorElective method of the Course class must be empty. 
+	} 
+
+	public static void testBase()  
+	{ 
+		Base b = new Base("DS1001", "EntryCourse"); 
+		System.out.println(b.getCode() == "DS1001"); 
+		System.out.println(b.getTitle() == "EntryCourse"); 
+		System.out.println(b.getPreRequisite() == b); 
+	} 
+  
+	public static void main(String[] args)  
+	{ 
+		testCourse(); 
+		testMajorElective(); 
+		testMajorRequired(); 
+		testBase(); 
+	} 
+  
+
+  
+} 
diff --git a/assignment4/Question5/StartGrading.java b/assignment4/Question5/StartGrading.java
new file mode 100644
index 0000000..1f95661
--- /dev/null
+++ b/assignment4/Question5/StartGrading.java
@@ -0,0 +1,64 @@
+public class StartGrading {
+	public static void testCourse() 
+	{	//Since we cannot create any Course object, 
+		//the testAnimal method of the Course class must be empty.  
+	}
+	
+	public static void testMajorRequired()  
+	{   
+		//create a Base object 
+		Base b = new Base("DS1001","EntryCourse"); 
+		//create a first MajorRequired object with the base course as pre-requisite 
+		MajorRequired mr1 = new MajorRequired("DS200X","OOP",b); 
+		//create a second MajorRequired object with the first major required course as pre-requisite 
+		MajorRequired mr2 = new MajorRequired("DS300X","Data Mining",mr1); 
+		 
+		//test mr1 
+		System.out.println(mr1.getCode()=="DS200X"); 
+		System.out.println(mr1.getTitle()=="OOP"); 
+		System.out.println(mr1.getPreRequisite() == b); 
+		 
+		//test mr2 
+		System.out.println(mr2.getCode()=="DS300X"); 
+		System.out.println(mr2.getTitle()=="Data Mining"); 
+		System.out.println(mr2.getPreRequisite() == mr1); 
+    }
+
+	public static void testMajorElective()  
+	{   
+		//create a Base object 
+		Base b = new Base("DS1001","EntryCourse"); 
+		//create a first MajorRequired object with the base course as pre-requisite 
+		MajorRequired mr1 = new MajorRequired("DS200X","OOP",b); 
+		//create a MajorElective object with the major required course as pre-requisite 
+		MajorElective me1 = new MajorElective("DS300X","Data Mining",mr1); 
+		 
+		//test mr1 
+		System.out.println(mr1.getCode()=="DS200X"); 
+		System.out.println(mr1.getTitle()=="OOP"); 
+		System.out.println(mr1.getPreRequisite() == b); 
+		 
+		//test mr2 
+		System.out.println(me1.getCode()=="DS300X"); 
+		System.out.println(me1.getTitle()=="Data Mining"); 
+		System.out.println(me1.getPreRequisite() == mr1); 
+	} 
+	
+	public static void testBase()  
+	{ 
+		Base b = new Base("DS1001", "EntryCourse"); 
+		System.out.println(b.getCode() == "DS1001"); 
+		System.out.println(b.getTitle() == "EntryCourse"); 
+		//System.out.println(b.isRequired() == true); 
+		System.out.println(b.getPreRequisite() == b); 
+	} 
+
+
+	public static void main(String[] args)  
+	{ 
+		testCourse(); 
+		testBase(); 
+		testMajorRequired(); 
+		testMajorElective(); 
+	} 
+} 
diff --git a/assignment4/Question6/StartGrading.java b/assignment4/Question6/StartGrading.java
new file mode 100644
index 0000000..a69ce9d
--- /dev/null
+++ b/assignment4/Question6/StartGrading.java
@@ -0,0 +1,76 @@
+public class StartGrading {
+	public static void testCourse() 
+	{	//Since we cannot create any Course object, 
+		//the testAnimal method of the Course class must be empty.  
+	}
+	
+	public static void testMajorRequired()  
+	{   
+		//create a Base object 
+		Base b = new Base("DS1001","EntryCourse"); 
+		//create a first MajorRequired object with the base course as pre-requisite 
+		MajorRequired mr1 = new MajorRequired("DS200X","OOP",b); 
+		//create a second MajorRequired object with the first major required course as pre-requisite 
+		MajorRequired mr2 = new MajorRequired("DS300X","Data Mining",mr1); 
+		 
+		//test mr1 
+		System.out.println(mr1.getCode()=="DS200X"); 
+		System.out.println(mr1.getTitle()=="OOP"); 
+		System.out.println(mr1.getPreRequisite() == b); 
+		 
+		//test mr2 
+		System.out.println(mr2.getCode()=="DS300X"); 
+		System.out.println(mr2.getTitle()=="Data Mining"); 
+		System.out.println(mr2.getPreRequisite() == mr1); 
+    }
+
+	public static void testMajorElective()  
+	{   
+		//create a Base object 
+		Base b = new Base("DS1001","EntryCourse"); 
+		//create a first MajorRequired object with the base course as pre-requisite 
+		MajorRequired mr1 = new MajorRequired("DS200X","OOP",b); 
+		//create a MajorElective object with the major required course as pre-requisite 
+		MajorElective me1 = new MajorElective("DS300X","Data Mining",mr1); 
+		 
+		//test mr1 
+		System.out.println(mr1.getCode()=="DS200X"); 
+		System.out.println(mr1.getTitle()=="OOP"); 
+		System.out.println(mr1.getPreRequisite() == b); 
+		 
+		//test mr2 
+		System.out.println(me1.getCode()=="DS300X"); 
+		System.out.println(me1.getTitle()=="Data Mining"); 
+		System.out.println(me1.getPreRequisite() == mr1); 
+	} 
+	
+	public static void testBase()  
+	{ 
+		Base b = new Base("DS1001", "EntryCourse"); 
+		System.out.println(b.getCode() == "DS1001"); 
+		System.out.println(b.getTitle() == "EntryCourse"); 
+		//System.out.println(b.isRequired() == true); 
+		System.out.println(b.getPreRequisite() == b); 
+	} 
+
+	public static void testManyCourses() 
+	{ 
+		Base b = new Base("DS1001","EntryCourse"); 
+		MajorRequired mr1 = new MajorRequired("DS200X","OOP",b); 
+		MajorElective me1 = new MajorElective("DS300X","Data Mining",mr1); 
+		ManyCourses mc = new ManyCourses(); 
+		mc.addCourse(b); 
+		mc.addCourse(mr1); 
+		mc.addCourse(me1); 
+		mc.listCourses(); 
+	} 
+	
+	public static void main(String[] args)  
+	{ 
+		testCourse(); 
+		testBase(); 
+		testMajorRequired(); 
+		testMajorElective(); 
+		testManyCourses(); 
+	} 
+}