In a BCC structure $($see below schematic$),a=0\mathrm{.}35nm,$ the atomic weight of the material is $141g/$mol$,$ answer the following questions $(4$ points$).$

$1\mathrm{.}1.$ Draw a $[121\_]$ direction $(1$ point $)$

$1\mathrm{.}2$ Draw a $(210)$ plane $(1$ point $)$

$1\mathrm{.}3$ Calculate the theorical density of the material $(2$ points$).$