Final answer:
The force of the tabletop on the object is the normal force which is equal in magnitude and opposite in direction to the weight of the object.
Step-by-step explanation:
When an object rests on a horizontal surface, the force of the tabletop on the object is the normal force. The normal force is equal in magnitude and opposite in direction to the weight of the object. In this case, since the object weighs 4 newtons, the force of the tabletop on the object is also 4 newtons.