Refer to the data file P08_66.xlsx. Comfy Company sells mediumpriced patio furniture through a mailorder catalog. It has operated primarily in the East but is now expanding to the Southwest. To get off to a good start, it plans to send potential customers a catalog with a discount coupon. However, Comfy is not sure how large a discount is needed to entice customers to buy. It experiments by sending catalogs to selected residents in six cities. Tucson and San Diego receive coupons for 5% off any furniture within the next two months, Phoenix and Santa Fe receive coupons for 10% off, and Riverside and Albuquerque receive coupons for 15% off. Comfy wonders whether there are differences across pairs of cities that receive the same discount. a. Calculate a 95% confidence interval for the difference between the mean amount spent for the following pairs of cities: (These means should include the "D purchases.' Round your answers to one decimal place, if necessary. If your answer is negative number, enter "minus\" sign.) Lower Limit Upper Limit Tucson minus San Diego -139.9 a 5.9 a Phoenix minus Santa Fe 150.9 a 122.51 0 Riverside minus Albuquerque 0 0 Does city appear to make a difference? -9 b. Calculate a 95% confidence interval for the difference between the proportion of customers who purchase something for the following pairs of cities: (Round your answers to three decimal places, if necessary. If your answer is negative number, enter "minus" sign.) Lower Limit Upper Limit Tucson minus San Diego -202.8 0 68.8 0 Phoenix minus Santa Fe 0 0 Riverside minus Albuquerque a a Does city appear to make a difference? -9