4. As a car salesman, James earns a commission on every car he sells. The table below shows the commission he earns based on the number of cars he sells. Number of Commission Earned Cars Sold (in dollars) FUMES 2 600 3 900 5 1,500 8 2,400 12 3,600 How much commission does James earn on every one car sold? A. $100 B. $300 C. $600 D. $900