Equal volumes of three acid solutions of pH 3, 4 and 5 are mixed in a vessel. What will be the $H^+$ ion concentration in the mixture ?

Question

$\begin {array} {1 1} (1)\;1.11 \times 10^{-3}M & \quad (2)\;1.11 \times 10^{-4}M \\ (3)\;3.7 \times 10^{-4}M & \quad (4)\;3.7 \times 10^{-3}M \end {array}$