A sum of money place at compound interest doubles itself in 3 years. In how many years will it amount to eight times itself?	Choose the correct choice.
A) 7  B) 8  C) 9  D) 10  E) 11
100 ---- 200 ---- 3   400 ---- 3   800 ---- 3   ------   9 years   Answer: 9
<result>C</result>
A sum of money place at compound interest doubles itself in 3 years. In how many years will it amount to eight times itself?