As you know by now the convergent-divergent nozzle is a central element in the generation of supersonic gas flows. In the following example, pressurized air is expanded through a convergent-divergent nozzle. The length of the nozzle is 0.8 m, and the throat is located 0.25 m from the nozzle inlet. When the nozzle pressure ratio (NPR) is 1.5, i. e., the inlet total pressure is 1.5 times the pressure downstream of the nozzle exit, there is a normal shock at the nozzle exit. Note! you will most likely need to use iterative methods to solve the problems below (3p.) Calculate the nozzle area ratio (exit area over throat area) (2p.) Calculate the NPR (for the same nozzle geometry) for which choked conditions are reached but the flow through the entire nozzle is subsonic (1p.) Assume that we would have an NPR between the normal-shock-at-exit NPR (1.5) and the NPR defining lower limit of choked nozzle flow (the NPR obtained in the subtask above), would it be possible to use the area-Mach-number relation throughout the nozzle? Justify and explain why or why not