Consider a solid sphere $($e$.$g$.,$ a planet$)$ with mass $M$ and radius $R.$ The volume mass density for this planet is given by

$Ak\frac{g}{m^2}$AMRvec$(g)(r)r>R(r)r>R0$ and $r>R0$ and $r>R$

$(c)$ Determine the gravitational potential $(r)$ for all points $in$ the regions $0$ and $r>R$