The lifetimes of the tread of a certain automobile tire are normally distributed with mean 37,500 miles and standard deviation 4,500 miles. For each of the questions below make sure to show your work. Round any z-score calculated to two decimal places to find your result.
a. What percent of tires have a tread life between 33,000 and 42,000 miles?
b. The manufacturer wants to know what percent of times tread life is less than
30,000 miles.
c. Find the tread life for the 80th percentile. Round to nearest integer (if needed)