The equilibrium constant K for the reversible reaction A=B is 2 ×...

The equilibrium constant $K$ for the reversible reaction $A=B$ is $2 \times 10^3$ at $350 K$. The rate constants of the forward reaction in the presence and absence of a suitable catalyst at the same temperature are $5 \times 10^4 \mathrm{~s}^{-1}$ and $4 \times 10^{-6} \mathrm{~s}^{-1}$ respectively. The rate constant of the reverse reaction in the absence of the catalyst is