4-15. A 3-kVA, 220:110-V, 60-Hz single-phase transformer yields this test data: open-circuit test: 200 V, 1.4 A, 50 W short-circuit test: 4.5 V, 13.64 A, 30 W Determine the efficiency

when the transformer delivers a load of 2 kVA at 0.85 power factor lagging.