The transformer in a power brick (as used in a laptop computer) converts the AC voltage from a wall socket (V_rms = 120 V) to a value near 12 V.
(a) If the output coil of the transformer has 4000 turns, how many turns does the input coil have? 

(b) If this transformer were accidentally connected backward (with the input and output coils reversed), what would the output voltage be?