Solid State

Gold crystallises in fcc lattice. The edge length of the unit cell is $4 \mathop {\rm{A}}\limits^{\rm{o}}$. The closest distance between gold atoms is ' $x$ ' $\mathop {\rm{A}}\limits^{\rm{o}}$ and density of gold is ' $y$ ' $\mathrm{g} \mathrm{cm}^{-3}$. What are $x$ and $y$ respectively?

(Molar mass of gold $=197 \mathrm{~g} \mathrm{~mol}^{-1} ; N=6 \times 10^{23} \mathrm{~mol}^{-1}$ )