Assume that the average gas mileage of all automobiles is 21.6 miles per gallon. For a random sample of 40 sport utility vehicles. The mean gas mileage is 20.7 miles per gallon with a standard deviation of 3.8 miles per gallon. Test the claim that he mean mileage or all suvs is less than 21.6 miles per fallen and significance 0.05 significance level. Find the z score