Jayantilal, a shrewd investor, comes to know of two different investment schemes. Scheme A doubles the money in six years by simple interest at a certain rate. Scheme B doubles the money in six years at a different rate, but by compound interest. To keep his money safe, in case a scheme turns out to be a scam, he takes out the money after every 3 years from one scheme and puts into the other. If he starts with scheme A, in how many years will his money become 4.5 times?

6

8

9

12