Three charges are at rest on the z$-$axis: q$1=-5\mathrm{.}4$ mC at z $=+3\mathrm{.}11$ m$,$ q$2=2$ mC at z $=0$ m$,$ and q$3=-9\mathrm{.}2$ mC at z $=-4\mathrm{.}61$ m$.$ What is the potential energy of this system? The constant k is k $=9\backslash$times $109$ N$$m$2/$C$2.(-9258\mathrm{.}829740718$ J$)$