static void Main(string[] args)
{
var book = new Book
{
Name = "Grade Boo"
};
book.AddGrade(89.54);
book.AddGrade(56.8);
book.AddGrade(32.23);
var statistic = book.GetStatistic();
Console.WriteLine($"the low is {statistic.Low}");
Console.WriteLine($"the high is {statistic.High}");
Console.WriteLine($"the average is {statistic.Average:N}");
}
