write a program to calculate the average of all scores entered between 0 and 100. use a sentinel-controlled loop varible 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. This should be in C#