If the equilibrium constant for the reaction $ 2AB \rightleftharpoons A_2+B_2 \: is \: 49$, what is the equilibrium constant for $ AB \rightleftharpoons \large\frac{1}{2}\: A_2 + \large\frac{1}{2}B_2$?

Question

$\begin {array} {1 1} (1)\;7 & \quad (2)\;\large\frac{1}{7} \\ (3)\;24.5 & \quad (4)\;49 \end {array}$