Air, assumed to be a perfect gas from Table A.4, flows through a long, 2-cm-diameter insulated tube. At section 1, the pressure is 1.1 MPa and the temperature is 345 K. At section 2, 67 meters further downstream, the density is 1.34 kg/m3, the temperature 298 K, and the Mach number is 0.90. For one-dimensional flow, calculate (a) the mass flow; (b) p2; (c) V2; and (d) the change in entropy between 1 and 2. (e) How do you explain the entropy change?