A 15.0 kg rocket is to be launched vertically from the surface of a planet with mass 6.50 *10^23 kg, a radius of 3.50*10^6 m, and no atmosphere. if the rocket is launched with an initial kinetic energy of 7.20*10^7 J what will its kinetic energy (J) be when it is 4.50 *10^6 m from the center of the planet.