At WLU (a famous Canadian university), suppose that instructors mark exams out of 100 and then must convert that mark to a letter grade using the following conversions.

A: 80–100

B: 70–79.9

C: 60–69.9

D: 50–59.9

F: Less than 50

Student X’s marks on each course are 81, 83, 81, 71, 72, 74, 63, 61, 51, 35.

Student Y’s marks are 98, 96, 99, 79, 78, 79, 68, 69, 57, 49.

a. Calculate each student’s average mark.

b. Convert the individual marks into letter grades and calculate the grade point average where A = 4, B = 3, C = 2, D = 1, and F = 0.