The top selling Red and Voss tire is rated 70,000 miles, which means nothing, In fact, the distance the tires can run until they wear out is a normally distributed random variable with a mean of 82,000 miles and a standard deviation of 6,400 miles.
a. What is the probability that a tire wears out before 70,000 miles?
b. What is the probability that a tire lasts more than 100,000 miles?