A 400 kVA transformer has a primary winding resistance of 0.5 and a secondary winding resistance of 0.001 . The iron loss is 2.5 kW and the primary and secondary voltages are 5 kV and 320 V respectively. If the power factor of the load is 0.85, determine the efficiency of the transformer (a) on full load, and (b) on half load.

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