Task: Question Answering
Input (English): Problem: a and b can do a piece of work in 10 days , b and c in 15 days , c and a in 12 days . how long will c take to do it ? 
Options: a ) 70 days , b ) 55 days , c ) 24 days , d ) 40 days , e ) 11 days
Output (English): d