The average salary for graduates entering the actuarial field is $40,000 (). If the salaries are normally distributed with a standard deviation of $5000 (σ = 5000), find the probability that:
a. An individual graduate (n = 1) will have a salary over $45,000: P(X > 45,000).
b. A group of nine graduates (n = 9) will have an average over $45,000: P()