A 2.0-kilogram laboratory cart moving with a velocity of 0.250 meter per second due east collides with and sticks to a similar cart initially at rest. After the collision, the two carts move off together with a velocity of 0.125 meter per second due east. The total momentum of this frictionless system is (1) zero before the collision (2) zero after the collision (3) the same before and after the collision (4) greater before the collision than after the collision