Using diaries for many weeks, a study on the lifestyles of visually impaired students was conducted. The students kept track of many lifestyle variables including how many hours of sleep

obtained on a typical day. Researchers found that visually impaired students averaged 9.01 hours of sleep, with a standard deviation of 1.55 hours. Assume that the number of hours of sleep for these visually impaired students is normally distributed, (a) What is the probability that a visually impaired student gets less than 6 hours of sleep? (b) What is the probability that a visually impaired student gets between 6.1 and 7.53 hours of sleep? (c) Thirty percent of students get less than how many hours of sleep on a typical day?