A 4 kg/s steady flow of ammonia runs through a device where it goes through a polytropic

Question:

A 4 kg/s steady flow of ammonia runs through a device where it goes through a polytropic process. The inlet state is 150 kPa, -20oC and the exit state is 400 kPa, 80oC, where all kinetic and potential energies can be neglected. The specific work input has been found to be given as [n/(n-1)] Δ(Pv).
a) Find the polytropic exponent n
b) Find the specific work and the specific heat transfer.