More than 100 million people around the world are not getting enough sleep; the average adult needs between 7.5 and 8 hours of sleep per night. College students are particularly at risk of not getting enough shut-eye.

A recent survey of several thousand college students indicated that the total hours of sleep time per night, denoted by the random variableX, can be approximated by anormalmodel with E(X) =6.68hours and SD(X) =1.15hours.

Question 1. Find the probability that the hours of sleep per night for a random sample of 4 college students has a meanxbetween6.7and6.97.

(use 4 decimal places in your answer)

Question 2. Find the probability that the hours of sleep per night for a random sample of 16 college students has a meanxbetween6.7and6.97.

(use 4 decimal places in your answer)

Question 3. Find the probability that the hours of sleep per night for a random sample of 25 college students has a meanxbetween6.7and6.97.

(use 4 decimal places in your answer)