Assume there are 100 million passenger cars in the United States and that the average fuel consumption

Question:

Assume there are 100 million passenger cars in the United States and that the average fuel consumption is 20 mi/gal of Gasoline. If the average distance traveled by each car is 10 000 mi/yr, how much gasoline would be saved per year if average fuel consumption could be increased to 25 mi/gal?