A block of mass \(m\) is pushed up a rough incline at a constant speed by an external force of magnitude \(F_{ext}\) acting parallel to the incline. The block is moved from the bottom of the incline to a final height \(h\). Which of the following correctly compares the work done by the external force, \(W_{ext}\), to the change in the gravitational potential energy of the block-Earth system, \(\Delta U_g\), and provides a correct justification?