The S.I. on a certain sum of money for 2 years at 6% per annum is half the C.I. on Rs. 4000 for 2 years at 10% per annum. The sum placed on S.I. is?  Choose the correct answer.
A) 2197  B) 1267  C) 3500  D) 2267  E) 1262
Explanation:   C.I. = [4000 * (1 + 10/100)2 - 4000]   = (4000 * 11/10 * 11/10 - 4000) = Rs. 840.   Sum = (420 * 100)/(2 * 6) = Rs. 3500   Answer:3500
<result>C</result>
The S.I. on a certain sum of money for 2 years at 6% per annum is half the C.I. on Rs. 4000 for 2 years at 10% per annum. The sum placed on S.I. is?