Cart 1 of mass \(2M\) moves to the right with constant velocity \(v_0\) on a horizontal, frictionless track toward Cart 2 of mass \(M\), which is initially at rest. The carts collide and stick together. Which of the following graphs best represents the momentum \(p\) of Cart 1 (solid line) and Cart 2 (dashed line) as a function of time \(t\)?