In the design of an automobile radiator, an engineer has a choice of using either a brass-copper alloy casting or a plastic molding. either material provides the same service. however, the brass-copper alloy casting weighs 25 pounds, compared with 20 pounds for the plastic molding. every pound of extra weight in the automobile has been assigned a penalty of $6 to account for increased fuel consumption during the life cycle of the car. the brass-copper alloy casting costs