Air undergoes a polytropic expansion process in a piston-cylinder assembly from 75 psia and 300 F to 15 psia. Employing the ideal gas model with constant specific heat ratio k, determine the temperature at the end of the process and the amounts of work and the heat transfer per unit mass in Btu/lb if
a) n=1.3
b) n=k
with k=1.4 and R=0.0686 Btu/lbR