$7-49$ Refrigerant$-134$a enters an adiabatic compressor as saturated vapor at $160$ kPa at a rate of $2\frac{m^3}{m}in$ and is comoressed to a pressure of $900$ kPa $.$ Determine the minimum nwer that must be supplied to the compressor.

$9-65.$ The post has a square cross$-$sectional area. If it is fixed at its base and a horizontal force is applied at its end as shown, determine $($a$)$ the maximum in$-$plane shear stress developed at A and $($b$)$ the principal stresses at $A.$

Prob. $9-65$