The energies of activation for forward and reverse reaction for ${\mathrm{A}}_2+{\mathrm{B}}_2\rightleftharpoons 2\mathrm{AB}$ are 180 kJ ${\text{mol}}^{-1}$ and 200 kJ ${\text{mol}}^{-1}$ respectively. The presence of catalyst lowers the activation energy of both (forward and reverse) reactions by 100 kJ ${\text{mol}}^{-1}$. The enthalpy change of the reaction $\left({\mathrm{A}}_2+{\mathrm{B}}_2\to 2\mathrm{AB}\right)$ in the presence of catalyst will be (in kJ ${\text{mol}}^{-1}$):