Task: Question Answering
Input (English): Problem: a can do a job in 8 days and b can do it in 20 days . a and b working together will finish twice the amount of work in - - - - - - - days ? 
Options: a ) 21 ½ days , b ) 11 3 / 7 days , c ) 23 ½ days , d ) 12 ½ days , e ) none of these
Output (English): b