A hypothetical metal has FCC structure at $1000$K$.$ Gvf $=0\mathrm{.}9$ eV$,$ and kB $=1\mathrm{.}38$ x $10-23$ J$/$K$.$

$1$eV$=1\mathrm{.}602$ x $10-19$ J$,$ NA$=6\mathrm{.}022$ x $1023$ mol$-1,$ Calculate:

$(1)$ among how many metal atom, one vacancy will form?

$(2)$ among how many unit cell, one vacancy will form?

$(3)$ how many defects will form in one mole of the metal?