Suppose it takes at least 5 people to push a very heavy box up a 400-cm ramp. If there are actually 6 people there to help push, which ramp(s) could they use to get the box moved? (Assume no friction.) A. 200-cm ramp B. 400-cm ramp C. 800-cm ramp D. Either the 400-cm ramp or the 800-cm ramp would work.