A sum of money amounts to Rs. 9800 after 5 years and Rs. 12005 after 8 years at the same rate of simple interest. The rate of interest per annum is?  Choose the correct choice from the following answers
A) 22
B) 88
C) 12
D) 77
E) 87
S.I. for 3 years = (12005 - 9800) = Rs. 2205   S.I. for 5 years = Rs. 2205/3 * 5 = Rs. 3675.   Principal = (9800 - 3675) = Rs. 6125   Hence, rate = (100 * 3675) / (6125 * 5)= 
<gadget id="calculator">(100 * 3675) / (6125 * 5)</gadget>
<output>12</output>
12%   Answer: 12
<result>C</result>
A sum of money amounts to Rs. 9800 after 5 years and Rs. 12005 after 8 years at the same rate of simple interest. The rate of interest per annum is?