Calculating Mass from Weight and Distance

[majormuss]

Homework Statement

How can I find mass when weight and distance is given.(Note I can't use 9.8m/s^2 as my acceleration of gravity because the question is dealing distances that are extremely high from Earth's surface.And also how can i find the right acceleration at such heights?

Homework Equations

F=ma

The Attempt at a Solution

am stuck cos I know i can't use 9.8m/s^2.

 

[Fightfish]

Have you come across Newton's theory of gravitation?
$$F_{g} = \frac{Gm_{1}m_{2}}{r^2}$$