What is relation between gravitational potential at surface s centre of earth

Hint: assuming the Earth is a homogenous sphere, at any point inside that sphere the gravitational force is proportional to the mass of the sphere that lies closer to the center than that point, divided by the distance from the center of the Earth squared. Potential energy is the integral of that force with respect to dx (distance from the center) integrated over x=0 to x=R. Determine that integral, then figure the constant of integration that makes it consistent with the boundary condition that PE at the surface is -GMm/R_e. From this - what do you get for an expression of PE for a point inside the Earth, and specifically for x=0?