A particular natural gas consists, in mole percents, of 83.0% CH4, 11.2% C2H6, and 5.8% C3H8. A 385-L sample of this gas, measured at 22.6 °C and 739 mmHg, is burned at constant pressure in an excess of oxygen gas. How much heat, in kilojoules, is evolved in the combustion reaction?