Write a python program that opens an output file with the filename scores.txt, asks the user to enter test scores (-1 to end) of a class, and writes them to the file. The program then opens this file, reads scores from the file to display letter grade for each score and the average test score of the class. Write the following function in the program: Determine_grade: This function should accept a test score as an argument and return a letter grade for the score based on the following grading scale: Score Letter Grade ≥90 AA ≥85 BA ≥80 BB ≥75 CB ≥70 CC ≥65 DC ≥60 DD ≥0 F