I'd be grateful if someone can help me with this problem - Zero, a hypothetical planet, has a mass of 4.4 × 10^23 kg, a radius of 3.2 × 10^6 m, and no atmosphere. A 2.4 kg space probe is to be launched vertically from its surface. (a) If the probe is launched with an initial energy of 7.4 × 10^7 J, what will be its kinetic energy when it is 4.8 × 10^6 m from the center of Zero? (b) If the probe is to achieve a maximum distance of 8.9 × 10^6 m from the center of Zero, with what initial kinetic energy must it be launched from the surface of Zero? I started out by using the equation for energy which is E = KE + U (kinetic energy plus potential energy). So I got 7.4x10^7 = KE + (mGR). But I have 2 main problems: one is, do I use G = 6.67x10^-11? The second question is, I know there is something I have to do with the radius, but I don't exactly know what. Do I do mass of probe/R? I did that but still got the answer wrong...I know I'm doing something wrong with the radius. Thanks a lot. *If I get part a, I'm sure I can get the second part by myself.