The solubility product, $K_{sp}\: of Ag_2\: CrO_4$ is $3.2 \times 10^{-11}\: at T(K)$ . Its solubility in mol $L^{-1}$ is

Question

$\begin {array} {1 1} (1)\;4 \times 10^{-4} & \quad (2)\;2 \times 10^{-4} \\ (3)\;2 \times 10^{-3} & \quad (4)\;4 \times 10^{-6} \end {array}$