Two swimmers, alan and beth, start together at the same point on the bank of a wide stream that flows with a speed v. both move at the same speed c (where c v), relative to the water. alan swims downstream a distance l and then upstream the same distance. beth swims so that her motion relative to the earth is perpendicular to the banks of the stream. she swims the distance l and then back the same distance so that both swimmers return to the starting point. which swimmer returns first? note: first guess the answer