Gravitational problem, spacecraft orbital period

[y90x]

Homework Statement

I need help getting started with this problem

At what altitude above the surface of the Moon must a lunar module orbit in order to complete each orbit in 1 h 49 min 39 s?

Homework Equations

g= Gm/r^2 ?

The Attempt at a Solution

Not quite sure how to start or anything , any help would be nice

 

[gneill]

You need to research some additional items. Look in your notes and textbook for the topic of orbital periods. You should be able to find an equation that will give you the period, knowing the mass of the central body. So you'll need to look up the mass of the Moon, too...