A convergent$-$divergent nozzle designed for Mach number of $2\mathrm{.}5$ is operating at an off$-$design condition as shown in the

figure. At this condition a normal shock form in the convergent portion of the nozzle at a section at which the area is equal

to the half of the exit section. If the nozzle is exhausting into an environment with the pressure of $1$atm calculate the Mach

number right after the normal shock wave.