static void Main(string[] args)
        {
            List <Student>  allStudents  = new List <Student>();
            List <Exercise> allExercises = new List <Exercise>();

            Cohort cohort1 = new Cohort("Cohort 1");
            Cohort cohort2 = new Cohort("Cohort 2");
            Cohort cohort3 = new Cohort("Cohort 3");

            Exercise excercise1 = new Exercise(allExercises)
            {
                Name = "excercise1", Language = "C#"
            };
            Exercise excercise2 = new Exercise(allExercises)
            {
                Name = "excercise2", Language = "Js"
            };
            Exercise excercise3 = new Exercise(allExercises)
            {
                Name = "excercise3", Language = "C#"
            };
            Exercise excercise4 = new Exercise(allExercises)
            {
                Name = "excercise4", Language = "Js"
            };
            Exercise excercise5 = new Exercise(allExercises)
            {
                Name = "excercise5", Language = "C#"
            };
            Exercise excercise6 = new Exercise(allExercises)
            {
                Name = "excercise6", Language = "CSS"
            };

            //use method to add to cohort list and link cohort to student/teacher

            Student student1 = cohort1.AddNewStudent("Steve", "Stevens", "SoS");
            Student student2 = cohort1.AddNewStudent("Beve", "Bevens", "BoB");
            Student student3 = cohort2.AddNewStudent("Fleve", "Flevens", "FoF");
            Student student4 = cohort2.AddNewStudent("Creve", "Crevens", "CoC");
            Student student5 = cohort3.AddNewStudent("Shmeve", "Shmevens", "ShOSh");
            Student student6 = cohort3.AddNewStudent("Dreve", "Drevens", "DoD");
            // cohort1.AddNewInstructor("Zeve", "Zevens", "ZoZ", "C#");
            // cohort1.AddNewInstructor("Heve", "Hevens", "HoH", "C#");
            // cohort1.AddNewInstructor("Leve", "Levens", "LoL", "C#");

            Instructor instructor1 = cohort1.AddNewInstructor("Zeve", "Zevens", "ZoZ", "C#");
            Instructor instructor2 = cohort1.AddNewInstructor("Heve", "Hevens", "HoH", "C#");
            Instructor instructor3 = cohort1.AddNewInstructor("Leve", "Levens", "LoL", "C#");



            //each instructor assigns to methods to a student.

            instructor1.AssignExercise(excercise1, cohort1);
            instructor1.AssignExercise(excercise2, cohort1);
            instructor2.AssignExercise(excercise1, cohort2);
            instructor2.AssignExercise(excercise2, cohort2);
            instructor3.AssignExercise(excercise1, cohort3);
            instructor3.AssignExercise(excercise2, cohort3);
        }