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You are the science officer on a visit to a distant solar system. Prior to landing on a planet you measure its diameter to be 2.070E+7 m and its rotation to be 19.8 hours. You have previously determined that the planet orbits 1.590E+11 m from its star with a period of 368.0 Earth days. Once on the surface you find that the freefall acceleration is 13.00 m/s2. What is the mass of the planet (in kg)?
What is the mass of the star (in kg)?

Physics help please 
drwls,
G*Mp/R^2 = 13.00 m/s^2
G = 6.67*10^11 N*m^2/kg^2
Solve for the planet mass, Mp.
The mass of the star can be deduced from Kepler's Third Law, using the period and radius of the orbit.
For the formula, see
http://spiff.rit.edu/classes/phys440/lectures/kepler3/kepler3.html
You do not need to use the period of rotation.