Calculate the number of vacancies per cubic meter in some metal at $682C.$ The energy for vacancy formation is $0\mathrm{.}86$

eV$/$atom atom, while the density and atomic weight for this metal are $6\mathrm{.}49\frac{g}{c}{m}^3($at $682C)$ and $63\mathrm{.}61\frac{g}{m}ol,$ respectively.