Write a korn shell program that will continually allow the user to input a numeric average for a number of students. After each grade is input the program will output the letter grade for that student. It will continue to ask for more grades until the user enters -1 to stop. Once the user enters -1, have program output the numeric average for all students.

A sample run could be:

What is the next student's numeric average? 82 That student got a B for the semester. What is the next student's numeric average? 77 That student got a C for the semester. What is the next student's numeric average? 86 That student got a B for the semester. What is the next student's numeric average? 62 That student got a D for the semester. What is the next student's numeric average? 95 That student got a A for the semester. What is the next student's numeric average? -99 The average for all students is 80.4