write a program that...

Takes in one of the comma separated value text files in the gradebooks folder (see folder tree) of the user's choosing
Calculates the final grade average of each student's assignment in a class roster
Note: All students in one gradebook have the same number of assignments but you do not know which gradebook the user will choose
Determines whether the student has made an A, B, C, D, or F based on the calculated final grade average. Below are the requirements for each:
A: 90-100
B: 80-89
C: 70-79
D: 60-69
F: 0-59
Writes each student's name, that student's final grade average, and letter grade into a new comma separated value text file. For example:
Alice, 96, A
Bob, 78, C
Charlie, 89, B