For a given reaction, energy of activation for forward reaction $\left({\mathbf{E}}_{af}\right)$ is $80\mathrm{kJ}{\mathrm{mol}}^{-1}\cdot \mathrm{\Delta H}=-40\mathrm{kJ} {\mathrm{mol}}^{-1}$ for the reaction. A catalyst lowers $E_{af}$ to $20\mathrm{kJ} {\mathrm{mol}}^{-1}$ The ratio of energy of activation for reverse reaction before and after addition of catalyst is :