The number of unit cells present in 39 grams of potassium if its crystallizes as body centred cube is : ( N = Avogadro number , At.wt of potassium =39)

Question

$\begin {array} {1 1} (1)\;\large\frac{N}{4} & \quad (2)\;\large\frac{N}{2} \\ (3)\;\large\frac{N}{3} & \quad (4)\;N \end {array}$