Professor Elderman has given the same multiple-choice final exam in his Principles of Biology class for many years. After examining his records from the past courses he has taught, he finds that the scores have a mean = 64.5 and a standard deviation = 15.

a/What is the probability Professor Elderman's class has a student who scored at least 78?

b/What is the probability Professor Elderman's class of 36 students have a class average below 60?