$7-77.$ A stream of $0\mathrm{.}10$ lb$/$s of air enters a thermally insulated heat exchanger, at $50$ psia and $0\backslash$deg F and is heated to $160\backslash$deg F$.$ On the other hand, a mass flow of $0\mathrm{.}50$ lb$/$s of $134$a refrigerant enters in a saturated vapor state at $300$ psia. Disregarding pressure drops, determine $($a$)$ the state of the refrigerant at the outlet and its temperature, $($b$)$ the variation of air entropy, $($c$)$ the variation of entropy of the refrigerant $($d$)$ Is the process reversible, irreversible or impossible?