Write a letter Grade function that gets an average score as an argument and returns the letter grade. If the average score is 90 or more, return an A. 80 to 89 – return a B. 70 to 79 – return a C. 60 to 69 – return a D. If the average score is less than 60, return grade F. Write the main function to ask the user his/her name and the number of test scores he/she has. Then ask the user to input those test scores (using a loop only). Then find the average test score. Then call the letter Grade function to get the letter grade. Display the average score and the person’s letter grade.