A massless rope connects a box on a horizontal surface and a hanging stone as shown below. The rope passes over a massless, frictionless pulley. The box is given a quick tap so that it slides to the right along the horizontal surface. The figure below shows the block after it has been pushed while it is still moving to the right. The mass of the hanging stone is larger than the mass of the box. There is friction between the box and the horizontal surface. Free-body diagrams that a student has drawn to scale for the box and for the hanging stone are shown.

Four students discussing these free-body diagrams make the following contentions: Ali:“I think there is a problem with the free-body diagram for the hanging stone. The two forces should have the same magnitude.” Brianna: “But the stone is moving upward – there should be a larger force in that direction.” Carlos:“No, the diagram for the hanging stone is okay, but there is a problem with the diagram for the box. The frictional force is in the wrong direction.” Dante:“No, all three of you are wrong. Both free-body diagrams are correct because both show the way the objects would be accelerating.” With which, if any, of these students do you agree?