An article on the cost of housing in California that appeared in the San Luis Obispo Tribune (March 30, 2001) included the following statement: "In Northern California, people from the San Francisco Bay area pushed into the Central Valley, benefiting from home prices that dropped on average $4000 for every mile traveled east of the Bay area." If this statement is correct, what is the slope of the least-squares regression line, y ⁄ 5 a 1 bx, where y 5 house price (in dollars) and x 5 distance east of the Bay (in miles)? Explain.