Question A$3$: A converging nozzle with an exit area of $1\mathrm{.}0c{m}^2$ is supplied from a gas reservoir in which the stagnation pressure is $500$ kPa and the stagnation temperature is $1200$ K $.$ Calculate the mass flow rate for back $($exit$)$ pressures of $0,350$ and $\mathrm{.}500$ kPa if the gas is Oxygen $($ R $=259\mathrm{.}8\frac{J}{k}g-K,$ r$=1\mathrm{.}4).$ The flow may be assumed isentropic $($i$.$e$.$ no frictional losses$).$