13.24 Sleep. The distribution of hours of sleep per week night, among college students, is found to be Normally distributed, with a mean of seven hours and a standard deviation of one hour. Use this information and the 68–95–99.7 rule to answer the following questions.
(a) What percentage of college students sleep more than seven hours? More than eight hours?
(b) What range contains the middle 95% of hours slept per week night by college students?