The formula to calculate the gravitational force between two objects is F_g=\frac{GM_1M_2}{r^2},F g

=
r
2

GM
1

M
2



, where M_1M
1

and M_2M
2

are the masses of the objects, GG is the gravitational constant and rr is the distance between the objects. Solve for M_1M
1

in terms of F_g, F
g

, G, G, M_2M
2

and r. r.