static void Main(string[] args) { var book = new Book("James' Gradebook"); book.GradeAdded += OnGradeAdded; book.GradeAdded += OnGradeAdded; book.GradeAdded -= OnGradeAdded; book.GradeAdded += OnGradeAdded; book.AddGrade(89.1); book.AddGrade(90.5); var grades = new List <double>() { 12.7, 10.3, 6.11, 4.1 }; grades.Add(56.1); Console.WriteLine($"The average grade is {book.AverageGrade()}\nTheLowestGrade is {book.LowestGrade()}\nThe Highest Grade is {book.HighestGrade()}"); }