A metallic element has a cubic lattice .Each edge of the unit cell is $2A^{\large\circ}$.The density of the metal is $2.5gcm^{-3}$.The unit cells in 200g of the metal are ?

Question

$\begin{array}{1 1}1\times 10^{25}\\2\times 10^{15}\\3\times 10^{25}\\4\times 10^{25}\end{array}$