4. (20 points) Open System Energy Balances A fuel oil is burned with air in a boiler furnace. The combustion process produces 1500kW of thermal energy, of which 70% is transferred as heat to boiler tubes that pass through the furnace. The combustion products pass from the furnace to a stack at 650C. Water enters the boiler tubes as a liquid at 75C and 1 bar, and leaves the tubes as saturated steam at 40 bar. a. Draw a picture of your system. Label input and exit streams and include mass flow rate, temperature, and pressure. Use variables to define any unknowns. b. Determine enthalpies for water streams at appropriate conditions. See attached steam table. All enthalpy values in the steam table are in kJ/kg. c. Write the open system energy balance and eliminate unnecessary terms (include brief justifications). d. Determine the mass flow rate of saturated steam. Please give your answer in kg/hr