Problem
Write an Ada program to calculate exam statistics. The file Exam_Data.txt contains an unknown number of exam scores. Each exam score is a whole number between 0 and 100. A negative value is used as a sentinel after the last exam score. Display the average exam score (rounded to one decimal place) and the number of A's (scores between 90 and 100), B's (80 to 89), C's (70 to 79), D's (60 to 69), and E's (scores less than 60).