13.45 Predicting pizza sales A chain restaurant that specializes in selling pizza wants to analyze how y = sales for a customer (the total amount spent by a customer on food and beverage, in pounds) depends on the location of the restaurant, which is classified as inner city, suburbia, or at an interstate exit.

a. Construct indicator variables x1 for inner city and x2 for suburbia so you can include location in a regression equation for predicting the sales.

b. For part

a, suppose yn = 6.9 + 1.2x1 + 0.5x2. Find the difference between the estimated mean sales at inner-city locations and at interstate exits.