Task: Question Answering
Input (English): Problem: a boat sails 15 km of a river towards upstream in 5 hours . how long will it take to cover the same distance downstream , if the speed of current is one - fourth the speed of the boat in still water : 
Options: a ) 2 , b ) 3 , c ) 4 , d ) 5 , e ) 6
Output (English): b