In the modern era, tires last much longer than they used to. According to research, the life of tires has increased from 20,000 miles in 1970 to 80,000 miles in the recent decade. A wholesaler wants to estimate the life of a Goodyear tire. He examines a sample of 50 tires of the Goodyear brand and wants to test whether or not the above is true. Assume that the wholesaler tests these samples for their average life, and finds their average life to be 70,000 miles, with a standard deviation of 10,000 miles.

a. At 0.05 level of confidence, determine if there is evidence that the population mean is different from 70,000 miles.

b. Interpret the results for the wholesaler.