According to the Sleep Foundation, average night's sleep is 6.8 hours. Suppose the standard deviation is 0.6 hours and that the probability distribution is normal.
a. What is the probability that random selected person sleeps more than 8 hours?
b. What is the probability that random selected person sleeps 6 hours or less?
c. Doctors suggest getting between 7 and 9 hours of sleep each night. What percentage of population gets this much sleep?