4. [7 points] Suppose you open two savings accounts S and S2. Each pays 6% compounded monthly. You put $10,000 into S now. You also plan to deposit $500 into S2 at the beginning of each month. After how many full months will the amount of S2 become greater than that in S? (A) 2 years (B) 21 months (C) 22 months (D) None of the above