Living in the Environment 18th Edition by Tyler Miller,Scott Spoolman

Exercise 4

Under normal driving conditions an internal combustion engine in a car produces approximately 200 grams (0.2 kilograms, or 0.44 pounds) of CO 2 per kilometre driven. Assume that a city you are studying has 7 million cars and that each car is driven an average of 20,000 kilometers (12,400 miles) per year.
By what percentage, and by what average distance driven, would use of cars in the city have to be cut in order to reduce by half the annual carbon footprint calculated in question 1