In this assignment, you will implement a simplified gradebook. Your application should:
Ask for a student's name.
Ask for how many letter grades will be inputted.
After all of the valid letter grades are entered, display the student's grade point average (GPA).
Ask if there is another student to be entered. (If yes, then repeat this workflow. If no, end the program cleanly.)
Note that the student's grades are entered as letters, but the GPA calculation will require translating those grades to numerical values. Use the "standard" letter grade-to-number conversion:
A = 4
B = 3
C = 2
D = 1
F = 0
When doing this conversion, you must use a switch block. For the "default" case, output an "invalid grade" message and repeat the input request.
Also, your program must use at least one user-defined function (main does not count). You must define the function and actually use it in your program. You can use the function to prompt for input, calculate the average, etc. It's your choice, but you must have at least one function.