Working against a 1-km-per-hour current, some members of the Outing Club paddled 7 km up the Exeter River one Saturday last spring and made camp. The next day, they returned downstream to their starting point, aided by the same one-km-per-hour current. They paddled for a total of 6 hours and 40 minutes during the round trip. Use this information to figure out how much time the group would have needed to make the trip if there had been no current.