Task: Question Answering
Input (English): Problem: it was calculated that 50 men could complete a piece of work in 10 days . when work was scheduled to commence , it was found necessary to send 25 men to another project . how much longer will it take to complete the work ? 
Options: a ) 20 days . , b ) 15 days . , c ) 22 days . , d ) 30 days . , e ) 18 days .
Output (English): a