Equilibrium constant for the reaction $\mathrm{H_2O(g) + CO(g) \rightleftharpoons H_2(g) + CO_2(g)}$ is 81. If velocity constant of the forward reaction is $162\text{ L mol}^{-1}\text{s}^{-1}$. What is the velocity constant (in $\text{L mol}^{-1}\text{s}^{-1}$) for the backward reaction?