Given ,$\mathrm{a}=4\times {10}^{-8} \mathrm{cm}$

$\mathrm{d}=9.03 \mathrm{g}/\mathrm{ml}$

$\mathrm{d}=\frac{\mathrm{ZM}}{{\mathrm{N}}_{\mathrm{A}}{\mathrm{a}}^3}$

Volume of a unit cell = a³, where a is the edge length

d is the density of the solid substance and M is the molar mass.

Mass of the unit cell = number of atoms in unit cell × mass of each atom =$\mathrm{Z}\times \mathrm{m}$

(Here z is the number of atoms present in one unit cell and m is the mass of a single atom)$\mathrm{M}=\frac{9.03\times 6.02\times {10}^{23}\times 64\times {10}^{-24}}{4}=86.97\mathrm{g}/\mathrm{mol}$