Answer:Since the cart is moving at a constant velocity, the net work done on the cart and the box is zero. This is because the net force acting on the cart and the box is zero, as there is no acceleration.
To understand why this is the case, we can use the work-energy theorem, which states that the net work done on an object is equal to its change in kinetic energy. Since the cart and the box are moving at a constant velocity, their kinetic energy is constant and there is no change in kinetic energy. Therefore, the net work done on the cart and the box is zero.
In summary, the net work done on the cart and the box is zero.