Write a program to calculate the average of all scores entered between 0 and 100.

Use a sentinel-controlled loop variable to terminate the loop. After values are entered and the average calculated, test the average to determine whether an A, B, C, D, or F should be recorded. The scoring rubric is as follows:

A—90-100; B—80-89; C—70-79; D—60-69; F < 60.