Answer
The net amount of work is zero in both cases.
Work Step by Step
In the case of the circular orbit, the net work done on the planet is the change in its kinetic energy. Because the speed is constant, the KE stays constant and the net work done is zero between any 2 points in the orbit.
In the case of the elliptical orbit, when the planet returns to its original position, it is traveling at the same speed as it was before, according to Kepler’s second law (sector velocity is constant). For a complete orbit, the net work done is zero.
