A sum of money place at compound interest doubles itself in 4 years. In how many years will it amount to eight times itself?  Choose the correct answer:
A) 17 years B) 62 years C) 12 years D) 16 years E) 52 years
100 ---- 200 ---- 4   400 ---- 4   800 ---- 4   ------   12 years   Answer: 12 years
<result>C</result>
A sum of money place at compound interest doubles itself in 4 years. In how many years will it amount to eight times itself?