400 KVA 34000/400 V transformer has copper losses is 5000 W and iron losses is 1000 W under nominal load and nominal voltage. A) Calculate the efficiency of the transformer when the nominal load is connected to the secondary of the transformer, power factor is 0.8? B) By using approximated equivalent circuit, when the primary voltage decreases to half, what is the value of new copper loss and new iron loss? C) By using approximated equivalent circuit, when the primary voltage increased by % 15, what is the value of new copper loss and new iron loss? D) By using approximated equivalent circuit, when the Snew = 200 KVA, what is the value of new copper loss and new iron loss?