static void Main(string[] args)
{
GradeAddedDelegate logger = (object sender, EventArgs eventArguments) => {
Console.WriteLine($"GradeAdded: {sender.ToString()}");
};
var demo = new Book("Demo");
demo.GradeAdded += logger;
demo.GradeAdded += GradesCounter;
demo.AddGrade(95);
demo.AddGrade(50);
demo.AddGrade(90);
demo.AddGrade(100);
demo.AddGrade(83.3);
Console.WriteLine($"Grades Added: {counter}.");
Console.WriteLine(demo.ToString());
Console.WriteLine(demo.GetStatistics().ToString());
}
