The Sanchez family wants to sell their house, which is 2800 square feet in size.

Mr. Sanchez notices that the slope of the least-squares regression line for predicting price from size is 0.0992. He says that if they put a 250-square-foot addition on their house, the selling price will increase by (0.0992)(250) = 24.8 thousand dollars, or

$24,800. Is this necessarily a good prediction? Explain.