A two-winding, 15-kVA, 2300:115-V, 60-Hz, single-phase transformer, which is known to have a core loss of 75 W and a copper loss of 250 W, is connected as an autotransformer to step up 2300 V to 2415 V. With a load of 0.8 power factor lagging, what kVA load can be supplied without exceeding the current rating of any winding? Determine the efficiency at this load.