4) (10%) Determine the internal energy of steam at 600 kPa and 0.375 m/kg if the enthalpy is 2749 kJ/kg. 5) (15%) Air in an internal-combustion engine has 227C, 1000 kPa, with a volume of 0.1 m. Combustion heats it to 1800K in a constant-volume process. What is the mass of air, and how high does the pressure become? 6) (15%) A gas expands in a piston from an initial pressure of 1000 kPa and an initial volume of 0.15 m to a final pressure of 200 kPa while following the process described by p=aV+b, where a = -1600 kPa/m and b is a constant. Calculate the work performed.