BCC iron with lattice parameter a $-0\mathrm{.}2866nm$ has electrical conductivity $=9\mathrm{.}71{10}^{-8}m$ at room temperature. Using a free clectron model and assuming three valence electrons per atom, calculate: $($i$)$ the concentration of conduction electrons, and $($ii$)$ the relaxation time.

Given that $m=2\mathrm{.}11{10}^{-11}kg$ and $e=1\mathrm{.}6{10}^{-14}C.$