A report in 2010 indicates that Americans between the ages of 8 and 18 spend an average of m 5 7.5 hours per day using some sort of electronic device such as smart phones, computers, or tablets. Assume that the distribution of times is normal with a standard deviation of s 5 2.5 hours and find the following values.

a. What is the probability of selecting an individual who uses electronic devices more than 9 hours a day?

b. What proportion of 8- to 18-year-old Americans spend between 8 and 12 hours per day using electronic devices? In symbols, p(8 , X , 12) 5 ?