A 500-V, single phase synchronous motor gives a net output mechanical power of 7.45kW and operates at 0.9 p.f. lagging. Its effective resistance is 0.8̦. If the iron and friction losses are 500W and excitation losses are 800W, a) Estimate the armature current. b) Calculate the commercial efficiency. c) If the synchronous motor is adjusted to operate at 0.85 p.f. lagging, calculate the commercial efficiency.