12.68 Bedrooms affect price? Refer to the previous exercise.

a. Explain what the regression parameter b means in this context.

b. Construct and interpret a 95% confidence interval for b.

c. Use the result of part b to form a 95% confidence interval for the difference in the mean selling prices for homes with x = 4 bedrooms and with x = 2 bedrooms. (Hint: How does this difference in means relate to the slope?)