In a population of college students, let X denote the number of hours that each student spends sleeping per week. Assume X is Normally distributed with mean mu = 50 hours and standard deviation sigma = 10 hours. a. What proportion of students that sleep less than 60 hours per week, i.e., what is the probability that X is less or equal to 60? b. What is the probability that X is more than 52.5? c. Find b such that the probability that X is less than or equal to b is 0.9713 i.e., what is b such that the area to the left of b is 0.9713