An element with molar mass $2.7 \times 10^{-2} \mathrm{~kg} \mathrm{~mol}^{-1}$ forms a cubic unit cell with edge length of $405 \mathrm{pm}$. If its density is $2.7 \times 10^3 \mathrm{~kg} \mathrm{~m}^{-3}$, the nature of cubic unit cell is :
$$
\left(\mathrm{N}_{\mathrm{A}}=6.02 \times 10^{23} \mathrm{~mol}^{-1}\right)
$$