Two carts have a compressed spring between them and are initially at rest. one of the carts has total mass, including its contents, of 5.0 kg, and the other has total mass of 3.0 kg. if the 3.0 kg cart is moving at 3.0 m/s after the spring is allowed to push the carts apart, what is the velocity of the 5.0 kg cart after release? the system is closed. a) -1.8 m/s b) -5.0 m/sc) -0.56 m/sd) -0.0 m/s