Suppose that the talk time on the Apple iPhone is approximately normally distributed with mean 7 hours and standard deviation 0.8 hour.
(a) What proportion of the time will a fully charged iPhone last at least 6 hours?
(b) What is the probability a fully charged iPhone will last less than 5 hours?
(c) What talk time would represent the cutoff for the top 5% of all talk times?
(d) Would it be unusual for the phone to last more than 9 hours? Why?