Refrigerant 134a is compressed adiabatically in a piston-cylinder assembly from saturated vapor at 10°F to a final pressure of 120 lbffin.?Determine the minimum theoretical work input required per unit mass

of refrigerant, in Btu/lb. \left(-\frac{W}{m}\right)_{\min }=12.78 \mathrm{Btu} / \mathrm{lb}