Task: Question Answering
Input (English): Problem: if the sample interest on a sum of money 20 % per annum for 2 years is $ 400 , find the compound interest on the same sum for the same period at the same rate ? 
Options: a ) $ 460 , b ) $ 510 , c ) $ 440 , d ) $ 500 , e ) $ 550
Output (English): c