3. exhaust gas from a chemical process flows at a rate of 8000 acfm from point a at 250 degrees f and 1 atm pressure. it is flows through a circular duct to a fan where the pressure is boosted by 4 inches of water and then flows to an incinerator. fuel gas is burned at a rate of 75 pounds per hour and the temperature of the exhaust gas is 1200 degrees f. assuming both the process exhaust and incinerator exhaust streams have properties similar to air, calculate the enthalpy that has been added by burning the fuel gas. assume that you can recover heat from the incinerator exhaust by purchasing aheat exchanger to cool the gases to 500 degrees f while recovering the useful heat. assuming that such heat is worth $7/million btu, how much money could you save by recovering the heat ($/day)