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 7 miles per day and it will take them two days, how many miles long is the route down the mountain ?
Options: a. 18, b. 19, c. 20, d. 21, e. 22
Output (English): d