Task: Question Answering
Input (English): Problem: a garrison of 400 men had a provision for 31 days . after 20 days 180 persons re - enforcement leave the garrison . find the number of days for which the remaining ration will be sufficient ? 
Options: a ) 65 days , b ) 45 days , c ) 20 days , d ) 16 days , e ) 18 days
Output (English): c