Residential real estate prices depend, in part, on property size and number of bedrooms. The house size X1 (in hundreds of square feet), number of bedrooms X2, and house price Y (in thousands of dollars) of a random sample of houses in a certain county were observed. The data are listed in the following table.

Use the accompanying output to answer the following questions.
a. Determine the least-squares estimates for the model in which house price is regressed on both house size and number of bedrooms. Find the predicted average price of a 2,500-square-foot home that has four bedrooms.
b. Compare the R2-value for the regression in part (a) with the r2 value for the data in Problem 16 of Chapter 5. Does adding X2 to a model that already contains X1 appear to be useful in predicting the house price?