Suppose that a category of world class runners are known to run a marathon (26 miles) in an average of 141 minutes with a standard deviation of 13 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 140 and 144 minutes in these 49 marathons. (Round your answer to four decimal places.)

b) Find the 70th percentile for the average of these 49 marathons. (Round your answer to two decimal places.) (in minutes