# A crystalline solid substance has a density of $10 g/cm^3$ and the length of the edge of the unit cell (FCC) is 2.0 A. How many number of atoms are present in 200 grams of the solid ?

$\begin {array} {1 1} (1)\;2 \times 10^{23} & \quad (2)\;1 \times 10^{26} \\ (3)\;1 \times 10^{25} & \quad (4)\;5 \times 10^{27} \end {array}$