Astronomy/math question?

Question

Assume the world is a spherical planet with a diameter of 1600 km with a uniform density of 5200 kilograms per cubic metre. If the moon is in a geostationary orbit around the world, and assuming a planets sidereal day is exactly 24 hours, how far is that geostationary orbit above the surface of the world?

Please submit your answer in kilometres, and round to the nearest kilometre. Submit only a number; any additional information may disqualify your entry.

Answer 1

For some reason, this same question has been asked 36 times. See if you can find a previous answer from this list:

http://answers.yahoo.com/search/search_r...

Answer 2

Earth - Moon system Roche Limit = 9,496 km.