Help with physics problem??

[Tall Man]

i'm having trouble calculating this problem. any help is appreciated

(Note: In this problem, you should a decimal place or two throughout your calculations, to prevent possible roundoff errors accumulating.)

Based on the following data about planet X:

Planet X's radius = 1.5·10^6^ m
Planet X's mass = 7.5·10^22^ kg

a.) Find gx, the acceleration due to gravity on the surface of Planet X. Answer in m/s^2^
b) What is the weight of a 10 kg ball on the surface of Planet X? Answer in N
c)How long would it take for the ball to hit the ground, if it was dropped from a height of 2 m ? Answer in s
d.) There is a moon in circular orbit of radius 4·10^8^ m around Planet X. How fast must the moon be going?
Answer in m/s
e)How long does it take for Planet X's moon to orbit once? (Your answer will come out in seconds.)
Answer in s
f) Based on the answer from e) how many (Earth) days is that?