With the partial oxidation of O$-$xylene, the reaction will take place with $80\%$ conversion under V$2$O$5$ catalyst. Phthalic anhydride with $80\%$ selectivity, maleic anhydride with $11\%$ selectivity, benzoic acid with $0\mathrm{.}5\%$ selectivity and combustion reactions with $8\mathrm{.}5\%$ selectivity. What is the energy balance for the isothermal reactor for these conditions?