A surveyor measures of heights of buildings in the city. He has determined that average heights of buildings in the city is 55 ft., and that the standard deviation of his measurements is 18 ft.
(a) If 25 measurements are selected at random, determine the probability that the average height of the 25 buildings is greater than 52 ft.
(b) if 36 measurments are selected at random, determine the probability that the average height of the 36 buildings is less than 50 ft.