A sum of money place at compound interest doubles itself in 6 years. In how many years will it amount to eight times itself?  Answers:
A) 6  B) 12  C) 18  D) 24  E) 30
100 ---- 200 ---- 6   400 ---- 6   800 ---- 6   ------   18 years   Answer: 18
<result>C</result>
A sum of money place at compound interest doubles itself in 6 years. In how many years will it amount to eight times itself?