Given a sample mean (xbar) of 8.7 and a population standard deviation (sigma) of 2.1 from a previous study where 21 vehicles where tested, find the z value and p value. The data indicates that the population mean for new tires improves a vehicle's quarter mile by 2 seconds. The mean for the current record for a vehicle with new tires is 8 seconds than a vehicle with old tires. The CEO of the company thinks that it can be lower based on our data. Test the claim that < 8.