Problem
Suppose a course has a final exam worth 50% of the final grade and two term tests worth 25% each. Write a function that takes in a vector of three percentage scores (Term Test 1, Term Test 2, Final Exam), calculates the student's final percentage grade and determines their letter grade using the letter grade cutoffs in our course syllabus. The function should return a list, where the first element of the list is the student's final percentage grade and the second element of the list is the student's letter grade.