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 were obtained on a typical day. researchers found that visually impaired students averaged 9.87 hours of sleep, with a standard deviation of 1.1 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 6.1 hours of sleep? b. what is the probability that a visually impaired student gets between 6.5 and 7.89 hours of sleep?