3. Smartphones come with an app that keeps track of the amount of time that the phone is being used. For teenagers, the distribution of amount of time they use their phone is approximately normal with mean = 7.75 hours per day and standard deviation = 1.25 hours per day.
(a) What percent of teenagers use their phone less than 5 hours per day?
(b) What percent of teenagers use their phone more than 10 hours per day?
(c) What proportion of teenagers use their phone between 6 to 8 hours per day?
(d) What is the 75th percentile of this distribution?
