Compound interest earned on a sum for the second and the third years are Rs.1200 and Rs.1440 respectively. Find the rate of interest?	Select the correct option:
A) 80% p.a	B) 50% p.a	C) 20% p.a	D) 27% p.a	E) 23% p.a
Rs.1440 - 1200   = Rs.240 is the interest on Rs.1200 for one year.   Rate of interest   = (100 * 240) / (100 * 1)   = 20% p.a   Answer:20% p.a
<result>C</result>
Compound interest earned on a sum for the second and the third years are Rs.1200 and Rs.1440 respectively. Find the rate of interest?