Satellite Orbit of the Moon

Homework Statement

The gravitational field strength on the moon, which has a radius of 1.74 x 10^6 m, is
approximately 0.17 as large as the gravitational field strength at the surface of the earth. The satellite is at an altitude of 100km above the moon.

What is the radius of the orbit of the satellite?

Homework Equations

I thought I would use the T^2/R^3= 4pi^2/GM

The Attempt at a Solution

That's just the thing. There is no period or mass in the problem, so I'm not sure how to solve this.