A converging-diverging nozzle with a rectangular cross-section and exit area ratio AAee⁄AAtt = 4.0 operates in an under-expanded condition. The working gas is air, the back pressure away from the nozzle exit is ppaa = 10 kPa, and the stagnation pressure is pp0 = 500 kPa. The exit pressure is greater than the back pressure (ppee > ppaa), so expansion waves form outside the exit. For the given conditions, what is the Mach number on the downstream side of the first set of expansion waves, and what is the turning angle?