A national homebuilder builds single‐family homes and
condominium‐style townhouses. The Excel file House Sales provides
information on the selling price, lot cost, type of home, and
region of the country (M = Midwest, S = South) for closings during
one month.

a. Develop a multiple regression model for sales price as a
function of lot cost and type of home.

b. Determine if any interactions exist between lot cost and type
of home, and find the best model.

c. Develop a regression model for selling price as a function of
lot cost and region. (Note that the cat-egorical variable region
has more than two levels.)