A three phase transformer, 200 MVA, 230/115 kV, Y-Y, has a resistance of 0.01 pu and a reactance of 0.05 pu. The excitation branch elements are Re = 100 pu and XM = 10 pu. The transformer supplies a load of 60 MVA at 0.80 PF lagging, do the following: 1. Draw the phasor diagram of one phase of the transformer. 2. Calculate the voltage regulation of the transformer under the above conditions. 3. Sketch the equivalent circuit referred to the low-voltage side of one phase of this transformer. 4. Calculate the efficiency of the transformer under the above condition.