13.49 Comparing revenue An entrepreneur owns two filling stations—one at an inner city location and the other at an interstate exit location. He wants to compare the regressions of y = total daily revenue on x = number of customers who visit the filling station, for total revenue listed on a daily basis at the inner city location and at the interstate exit location.

Explain how you can do this using regression modeling

a. With a single model, having an indicator variable for location that assumes the slopes are the same for each location.

b. With separate models for each location, permitting the slopes to be different.