The figure depicts two carts set on a flat track. On the left is a smaller cart labeled capital A with a rightward velocity labeled lower-case v subscript zero. On the right there is a larger block labeled capital B. Two carts are set on a flat track and roll without friction. Cart A rolls with initial velocity v­0 toward cart B which is at rest. The center of mass of the two-cart system has a velocity vcm, i before the carts collide and vcm, f after the carts collide. In which of the following situations will vcm, i = vcm, f?