Identical satellites X and Y of mass m are in circular orbits around a planet of mass M. The radius of the planet is R. Satellite X has an orbital radius of 3R, and satellite Y has an orbital radius of 4R. The kinetic energy of satellite X is Kx.

1) In terms of Kx, the gravitational potential energy of the planet-satellite X system is
(A) -2Kx
(B) -Kx
(C) -Kx/2
(D) Kx/2
(E) 2Kx

2) Satellite x is moved to the same orbit as satellite Y by a force doing work on the satellite. In terms of Kx, the work done on satellite X by the force is
(A) -Kx/2
(B) -Kx/4
(C) 0
(D) +Kx/4
(E) +Kx/2