Bob sells tires. He knows that his weekly sales drop if he increases the unit price p (in dollars). The weekly sales are given by an unknown function N(p). His weekly revenue is R(p)=pN(p). Bob is currently selling tires for 100 dollars each. His weekly sales are running at 120 tires per week, so N(100)=120. His marketing department estimates that he will lose 2 sales per week for each 10 dollar increase in unit price, so N′(100)=−0.2. Estimate Bob's increase in weekly revenue for each one dollar increase in tire price.