An AC adapter for a telephone-answering unit uses a transformer to reduce the line voltage of 120 V (rms) to a voltage of 9.0 V. The rms current delivered to the answering system is 400 mA.
(a) If the primary (input) coil in the transformer in the adapter has 240 turns, how many turns are there on the secondary (output) coil?
(b) What is the rms power delivered to the transformer? Assume an ideal transformer.