Task: Question Answering
Input (English): Question: A part of certain sum of money is invested at 9% per annum and the rest at 21% per annum, if the interest earned in each case for the same period is equal, then ratio of the sums invested is?

 Option A: 4:2

 Option B: 4:8

 Option C: 7:3

 Option D: 4:0

 Option E: 4:9
Output (English): Option C