For a reversible reaction $\mathrm{A}\rightleftharpoons \mathrm{B}\text{ the }{\mathrm{\Delta H}}_{\text{forward reaction }}=20\mathrm{KJ}{\mathrm{mol}}^{-1}$. The activation energy
of the uncatalysed forward reaction is 300 KJ mol ^-1.when the reaction is catalysed keeping the reactant concentration same, the rate of catalysed forward reaction at 27^oC found to be same as that of the uncatalysed reaction at 327^oC . The activation energy of the catalysed backward reaction is ____KJ mol ^-1