The tread lives of the Super Titan radial tires under normal driving conditions are normally distributed with a mean of 40,000 mi and a standard deviation of 3000 mi. (Round your answers to four decimal places.)
a) What is the probability that a tire selected at random will have a tread life of more than 35,800 mi?
b) Determine the probability that four tires selected at random still have useful tread lives after 35,800 mi of driving. (Assume that the tread lives of the tires are independent of each other.)
