A converging-diverging nozzle with a 4:1 exit-area ratio and p0 = 500 kPa operates in an under expanded condition (case 1 of Fig. 9.12) as in Fig. P9.147. The receiver pressure is pa = 10 kPa, which is less than the exit pressure, so that expansion waves form outside the exit. For the given conditions, what will the Mach number Ma2 and the angle φ of the edge of the jet be? Assume k = 1.4 as usual.