Suppose that a category of world class runners are known to run a marathon (26 miles) in an average of 144 minutes with a standard deviation of 16 minutes. Consider 49 of the races. Let

X

= the average of the 49 races.

a. Find the probability that the average of the sample will be between 141 and 145 minutes in these 49 marathons

b. Find the 70th percentile for the average of these 49 marathons.

c. Find the median of the average running times.