4. A steam boiler heats liquid water at 100C to superheated steam at 2 MPa and 350"C. Propane fuel [CHe (g)) is burned at atmospheric pressure with 35 percent excess air. The fuel and air enter the boiler at 25C and the products of combustion leave at 350C. Firstly: Sketch the T-s diagram for the boler, and secondly: Calculate by parametric analysis (a) the amount of steam generated per unit of fuel mass burned, (b) the change in the exergy of the combustion streams, in kl/kg fuel, (c) the change in the exergy of the steam stream, in kl/kg steam, and (d) the lost work potential, in k/kg fuel. Take To 25 C, and assume air, fuel and products have constant C, at average temperature. (S Points)