Suppose that a category of world class runners are known to run a marathon (26 miles) in an average of 142 minutes with a standard deviation of 15 minutes. Consider 49 of the races. Let

X

= the average of the 49 races. Find the probability that the average of the sample will be between139and143minutes in these 49 marathons. (Round your answer to four decimal places.)

• Part (c)Find the60thpercentile for the average of these 49 marathons. (Round your answer to two decimal places.) min