$-0\mathrm{.}2751$A uniformly charged spherical shell has inner and outer radii of $25\mathrm{.}0$ cm and $32\mathrm{.}0$ cm$,$ respectively. A point charge of $45\mathrm{.}0$ nC is located at the center of the spherical shell. A proton orbits around this arrangement just outside the spherical shell with a speed of $8\mathrm{.}26105$ m$/$s$.$ What is the volume charge density of the spherical shell? $($Include the sign of the value in your answer.$)$