Task: Question Answering
Input (English): Problem: a can do a piece of work in 80 days . he works at it for 10 days & then b alone finishes the remaining work in 42 days . in how much time will a and b , working together , finish the work ? 
Options: a ) 30 days , b ) 20 days , c ) 25 days , d ) 35 days , e ) 45 days
Output (English): a