Task: Question Answering
Input (English): Problem: a and b undertake to do a piece of work for $ 500 . a alone can do it in 5 days while b alone can do it in 10 days . with the help of c , they finish it in 2 days . find the share of c ? 
Options: a ) $ 200 , b ) $ 150 , c ) $ 300 , d ) $ 25 , e ) $ 100
Output (English): a