Consider a supersonic flow with an upstream Mach number of 4 and pressure of \(1 \mathrm{~atm}\). This flow is first expanded around an expansion corner with \(\theta=15^{\circ}\), and then compressed through a compression corner with equal angle \(\theta=15^{\circ}\) so that it is returned to its original upstream direction. Calculate the Mach number and pressure downstream of the compression corner.