Helium at 68 °f and 14.7 psia in a large tank flows steadily and isentropically through a converging nozzle to a receiver pipe. the cross-sectional area of the throat of the converging passage is 0.05 ft2. determine the mass flowrate through the duct if the receiver pressure is (a) 10 psia, (b) 5 psia. sketch temperature– entropy diagrams for situations (a) and (b).