A three-phase, four-pole, 220-V, 60-Hz induction machine with a per-phase resistance of 0.5 is operating at rated voltage as a generator at a slip of -0.04, delivering 12 A of line current and a total output of 4000W. The constant losses from a no-load run as a motor are given to be 220 W, of which 70 W represents friction and windage losses. Calculate the ef?ciency of the induction generator.