puck 1 of mass m1 = 0.30 kg is sent sliding across a frictionless lab bench, to undergo a one-dimensional elastic collision with stationary puck 2. Puck 2 then slides off the bench and lands a distance d from the base of the bench. Puck 1 rebounds from the collision and slides off the opposite edge of the bench, landing a distance 2.0d from the base of the bench. What is the mass of puck 2? (Hint: Be careful with signs.)