Task: Question Answering
Input (English): Problem: if a lends rs . 3500 to b at 10 % per annum and b lends the same sum to c at 15 % per annum then the gain of b in a period of 3 years is ? 
Options: a ) 525 , b ) 500 , c ) 510 , d ) 530 , e ) 550
Output (English): a