Isobutane (\(C_4H_{10}\)) is burnt completely in pure oxygen as per the reaction given below. Given that the standard heats of formation (in kcal/mole) of isobutane, carbon dioxide, and water vapour are -31.489, -94.052, and -60.150, respectively, the heat of reaction is ________ kcal (rounded off to 2 decimal places).
\[ C_4H_{10} + 6.5\,O_2 \to 4\,CO_2 + 5\,H_2O \]