The soda company sold 5,909,999,222 cans of soda last year. This year they sold 3,999,002,135 cans. Which is the best estimate of the total number of soda cans sold last year and this year?
A. 8,000,000,000
B. 9,000,000,000
C. 9,909,001,357
D. 10,000,000,000