Task: Question Answering
Input (English): Problem: a group of hikers is planning a trip that will take them up a mountain using one route and back down using another route . they plan to travel down the mountain at a rate of one and a half times the rate they will use on the way up , but the time each route will take is the same . if they will go up the mountain at a rate of 6 miles per day and it will take them two days , how many miles long is the route down the mountain ? 
Options: a ) 16 , b ) 17 , c ) 18 , d ) 19 , e ) 20
Output (English): c