12. The top-selling Red and Voss tire is rated 60000 miles, which means nothing. In fact, the distance the tires can run until wear out is a normally distributed random variable with a mean of 71000 miles and a standard deviation of 5000 miles. a. What is the probability that the tire wears out before 60000 miles? b. What is the probability that a tire lasts more than 81000 miles? 13. The following densiQy functiop describes a random variable X f (x) = (x 1)/8 if 1 < x < 5 a. Find the probability QhatXiies belween 2 and 4. b. Find the probability that is less fia 3 14, College students average 8.6 hours oi slee per night With a standard deviation of 35 minutes. If the amount of sleep is normallystributed what proportion of college students sleep for more than hours? 15. The following density function describe (18-x)/81 if a. Draw a graph of the densi n below: ii. iii. Find the probability p Find the prob?bllity a Find the probability that a ra dom vanable X. f(x) = (x1) if 0