private static void WriteResults(IGradeTracker book)
        {
            GradeStatisitcs stats = book.ComputeStatistics();

            WriteResult("Highest Grade", (int)stats.HighestGrade); //First method is used
            WriteResult("Lowest Grade", stats.LowestGrade);        //Second method is used
            WriteResult("Average Grade", stats.AverageGrade);      //Second method is used
            WriteResult(stats.Description, stats.LetterGrade);     //Third method is used
        }
        public override GradeStatisitcs ComputeStatistics()
        {                                                  /* This member method calculates  Avg, Min, and Max Grade
                                                            * It returns a variable of type GradeStatistics*/
            GradeStatisitcs stats = new GradeStatisitcs(); /* A variable of GradeStatistics type*/

            float sum = 0;

            foreach (float grade in grades)
            {
                sum += grade;
                stats.HighestGrade = Math.Max(grade, stats.HighestGrade); /*Math.Max returns the highest between two given values*/
                stats.LowestGrade  = Math.Min(grade, stats.LowestGrade);  /*Math.Min returns the lowest  between two given values*/
            }
            stats.AverageGrade = sum / grades.Count;                      /*grades.Count returns the number of items inside grades list*/
            return(stats);
        }