Air flows isentropically in a channel. Properties at section $1$ are v$1=250$ m$/$s$,$ t$1=330$ K$,$ and p$1$

$=80$ kPa. At section $2$ downstream, the temperature has dropped to $0$C$.$ Find $($a$)$ the pressure, $($b$)$

density, $($c$)$ velocity, and $($d$)$ Mach number at section $2.$