Since Newton's law of gravity and Coulomb's law have the same inverse-square dependence on distance, an expression

Question:

Since Newton's law of gravity and Coulomb's law have the same inverse-square dependence on distance, an expression analogous in form to Gauss's law can be found for gravity. The gravitational field g is the force per unit mass on a test mass m0. Then for a point mass m at the origin, the gravitational field g at some position r is

Compute the flux of the gravitational field through a spherical surface of radius r?centered at the origin, and show that the gravitational analog of Gauss's law is f_net = ?4?Gm_inside.