7. Assume constant acceleration. To reduce the drag coefficient and thus to improve the fuel efficiency, the frontal area of a car is to be reduced. Determine the amount of fuel and money saved per year as a result of reducing the frontal area from 17 to 14 ft2. Assume the car is driven 10,000 mi a year at an average speed of 55 mi/h. Take the density and price of gasoline to be 50 lbm/ft3 and $3.10/gal, respectively; the density of air to be 0.075 lbm/ft3; the heating value of gasoline to be 20,000 Btu/lbm; and the overall efficiency of the engine to be 30%