A professor's exam scores are approximately distributed normally with mean 78 and standard deviation 8.

a.) What is the probability that a student scores a 65 or less?

b.) What is the probability that a student scores a 90 or more?

c.) What is the probability that a student scores between 65 and 90?

d.) What is the lowest score a student must have in order to be in the top 5% of all student scores?