Liquid octane (C8H18) at 77°F, 1 atm enters a combustion chamber operating at steady state and burns completely with 50% excess dry air entering at 120°F, 1 atm. The products exit at 1700°F, 1 atm. Determine the magnitude of the rate of heat transfer between the combustion chamber and its surroundings, in Btu per lbmol of fuel entering. Kinetic and potential energy effects are negligible.