A certain quantity of electricity is passed through aqueous $AI_2\: (SO_4)_3\: and \: CuSO_4$ solutions connected in series. 0.09 g of $AI$ is deposited on cathode during electrolysis. The amount of copper deposited on cathode in grams is :

Question

$\begin {array} {1 1} (1)\;0.318 & \quad (2)\;31.8 \\ (3)\;0.636 & \quad (4)\;3.18 \end {array}$