Arule of thumb says reducing the compressor discharge pressure by 2 psi reduces the power input by 1%. show that this is true when the discharge pressure is reduced from 110 psig to 100 psig. hint: recall that for isentropic compression from absolute inlet pressure pi to absolute discharge pressure pe, the absolute temperature ratio te/ti = (pe/pi)^[(k-1)/k], where k = cp/cv = 1.4 for air. assume the mass flow rates and compressor efficiency are about the same for both discharge pressures.