The effective radius of the iron atom is $1.42\stackrel{°}{\mathrm{A}}$. It has FCC structure. Calculate its density $(\mathrm{Fe}=56\mathrm{amu})$.

The density of a pure substance '$\mathrm{A}$' whose atoms are packed in a cubic-close packed arrangement is $1 \mathrm{g} {\mathrm{cc}}^{-1}$. If $\mathrm{B}$ atoms can occupy tetrahedral void and all the tetrahedral voids are occupied by '$\mathrm{B}$' atoms, what is the density of resulting solid in $\mathrm{g} {\mathrm{cc}}^{-1}?$ $[$Atomic mass $\left(\mathrm{A}\right)=30 \mathrm{g} {\mathrm{mol}}^{-1}$ and atomic mass $\left(\mathrm{B}\right)=50 \mathrm{g} {\mathrm{mol}}^{-1}]$.