$[13]$ Chromium $(52\mathrm{.}00\frac{g}{m}ol)$ has a radius of $125pm$ and forms a bcc unit cell. What is the density of chromium in $\frac{g}{c}{m}^8$

$[14]$ The second$-$order diffraction $)=(2$ for a gold crystal is at an angle of $22\mathrm{.}20$ for $x-$rays of $154$ pm$.$ What is the spacing between these crystal planes.