Chapter 5, Problem 53PS

Write a program that determines a student's grade. It reads three test scores (between 0 and 100) and calls a function that calculates and returns a student's grade based on the following rules:

a. If the average score is $90\%$ or more, the grade is A.

b. If the average score is $70\%$ or more and less than $90\%,$ it checks the third score. If the third score is more than $90\%,$ the grade is A; other-wise, the grade is B.

c. If the average score is $50\%$ or more and less than $70\%,$ it checks the average of the second and third scores. If the average of the two is greater than $70\%,$ the grade is C; otherwise, it is D.

d. If the average score is less than 50 percent, then the grade is F.

The program's main is to contain only call statements. At least three subfunctions are required: one to read scores, one to determine the grade, and one to print the results.