A converging$-$diverging $($C$-$D$)$ nozzle with a throat area of $0\mathrm{.}2$ m$2$ and an exit area of $0\mathrm{.}3$ m$2$ is connected to a reservoir where air is kept at a $($stagnation$)$ pressure of $1345$ kPa and a temperature of $2760$ oC$.$ If the nozzle is operating such that a normal shock is positioned as shown, determine the Mach number of the air behind the normal shock $($ use $\backslash$gamma $=1\mathrm{.}4)$