Using magnetostatic pressure on a small patch of a uniform surface current of density k [current/width] why can we not analogous argument as griffiths did for electrostatic pressure, derive a formula for an regard this pressure [force/area] as being able to do work on the moving charges?

Atwo-stage air compressor operates at steady state, compression 10m^3/min of air from 100 kpa and 300k to 1200 kpa. an intercooler between the two stages cools the air to 300k at a constant pressure of 350 kpa. the compression processes are isentropic. a) calculate the power required to run the compressor, in kw b) compare the result to the power required for isentropic compression from the same inlet state to the same final pressure.