using C program

4. Write a function qualityPoints that accepts a student grade as a floating point number and returns 4 if it is above 90, 3 if it is above 80, 2 if it is above 70, 1 if it is above 60 and 0 below 60. The main() function should call this function and print out the letter grade A, B, C, D or F using a switch statement. The call should be within a loop that continuously queries for a grade from the keyboard input and exits only when the user enters -1