Task: Question Answering
Input (English): Problem: a certain number of men can finish a piece of work in 10 days . however , if there were 10 less men it will take 10 days more for the work to be finished . how many men were there originally ? 
Options: a ) 10 men , b ) 30 men , c ) 40 men , d ) 20 men , e ) none of these
Output (English): d