I would go with B.

Reason for that is;

2 _ _ _ _ = 24 different possibilities. The average of all such numbers would be close to 25,000.

4 _ _ _ _ = 24, average approx. 45,000

6 _ _ _ _ = 24. average approx. 65,000

8 _ _ _ _ = 24. average approx. 85,000

so 24(25000 + 45000 + 65000 + 85000) = 5160000 which is closest to B

just created a macro on excel to test the answer; and it comes to 5199960; The thing is; for all numbers beginning with 2, the average is 25000, but for all numbers beginning with 4, the average is less than 45000, and for all numbers beginning with 6, the average is even less than 65000 and for all numbers beginning with 8, it is less than 85000 by an amount greater than for 65000 or the others. It's an interesting question, though highly unlikely on the actual gmat.