64 Suppose that a category of world class runners are known to run a marathon 26 miles in an average of 145 minutes with a standard deviation of 14 minutes Consider 49 of the races Let X be the average of the 49 races a X b Find the probability that the runner will average between 142 and 146 minutes in these 49 marathons c Find the 80th percentile for the average of these 49 marathons d Find the median of the average running times