private static void WriteResults(IGradeTracker book) { GradeStatistics stats = book.ComputeStatistic(); book.AddGrade(6.5f); foreach (var grade in book) { Console.WriteLine(grade); } WriteResult("Highest grade", (int)stats.MaxGrade); WriteResult("Average grade", stats.AvgGrade); WriteResult("Lowest grade", stats.MinGrade); WriteResult("Your letter Grade is ", stats.LetterGrade); WriteResult("And it is ", stats.LetterGradeDescription); }