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()}");
}
