Task: Question Answering
Input (English): Question: A sum of money invested at compound interest amounts to Rs.800 in 3 years and to Rs.840 in 4 years. The rate of interest per annum is

 Option A: 2x1/2%

 Option B: 4%

 Option C: 5%

 Option D: 6x2/3%

 Option E: None
Output (English): Option C