During the first year at a university that uses a 4-point grading system, a freshman took ten 3-credit courses and received two As, three Bs, four Cs, and one D.
a. Compute this student's grade-point average.
b. Let the random variable X denote the number of points corresponding to a given letter grade. Find the probability distribution of the random variable X and compute E(X), the expected value of X.