3. (15 points) An auto shop claims that their tune-up service increases gas mileage. Fourteen randomly selected cars had their gas mileage measured before and after the tune-up, with the results (in miles per gallon) displayed in the table below. Test the auto shop's claim at the 1% significance level. Assume that the differences are normally distributed with no outliers. Hint: If we calculate the differences as After - Before, then H1: Ma > 0. If we calculate the differences as Before - After, then H1: Ma