physics

Zero, a hypothetical planet, has a mass of 3.0*10^23 kg, a radius of 3.0*10^6 m, and no atmosphere. A 10 kg space probe is to be launched vertically from its surface.
(a) If the probe is launched with an initial kinetic energy of 5.0*10^7 J, what will be its kinetic energy when it is 4.0*10^6 m from the center of Zero?
(b)If the probe is to achieve a maximum distance of 8.0*10^6 m from the center of Zero, with what initial kinetic energy must it be launched from the surface of Zero?

***for letter A, i got 2.335e8 by E = KE - GMm/R. What am i doing wrong?

thanks

SORRY FOR DOUBLE POST

On A, You have to remember that the change in PE is GMm/R - GMm/radius

Where R is 4.0*10^6 m and radius is the intial radius, or 3.0*10^6.

E= KEinitial -GMm/R + GMm/radius

On A, You have to remember that the change in PE is GMm/R - GMm/radius

Where R is 4.0*10^6 m and radius is the intial radius, or 3.0*10^6.

E= KEinitial -GMm/R + GMm/radius

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