=+d. With increasing fuel prices, the demand for hybrid cars that run partially on gasoline and partially on used cooking grease has increased. As a result, fast food chains report that they no longer have to pay to have grease picked up; in fact, they are increasingly being paid for their grease. (In essence, one of the goods you produce used to have a negative price but now has a positive price.) How does this change how many hamburgers are being produced at your fast food restaurant?