A horizontal force of 120N is required to push a bookcase across the floor at constant velocity. (a) What is the net force acting on the bookcase?

A horizontal force of 120N is required to push a bookcase across the floor at constant velocity. (a) What is the net force acting on the bookcase? (b) How much is the friction force that acts on the sliding bookcase? (c) How much friction acts on the bookcase when it is at rest on a horizontal surface without being pushed?