Compound interest earned on a sum for the second and the third years are Rs.2400 and Rs.2640 respectively. Find the rate of interest?  Select:
A) 10% p.a.	B) 20% p.a.	C) 15% p.a.	D) 12% p.a.	E) None of these.
Rs.2640 - 2400 = Rs.240 is the interest on Rs.2400 for one year.   Rate of interest = (240/2400) * 100= 
<gadget id="calculator">(240/2400) * 100</gadget>
<output>10</output>
10% p.a   10% p.a.NSWER:10% p.a.
<result>A</result>
Compound interest earned on a sum for the second and the third years are Rs.2400 and Rs.2640 respectively. Find the rate of interest?