A 1.0kg red cart is moving rightward with a speed of 60 m/s when it collides with a blue cart of equal mass that is initially at rest. The two carts stick together and move to the right with the same speed after the collision. What is the momentum of the red car before collision? O -60kgm/s O 30 kgm/s O O kgm/s O 60kgm/s