The figure shows three identical bulbs, an ideal battery and a switch S, open at first and then closed. Take each bulb's resistance as constant and brightness as proportional to power. (i) With S open, A and B are equally bright. (ii) On closing S, A becomes brighter. (iii) On closing S, B becomes brighter, since the battery supplies more current. (iv) On closing S, the battery current becomes $\dfrac{4}{3}$ of its first value. (v) On closing S, A is only twice as bright as B. How many are correct?

Fig. 1: A circuit with a battery of negligible internal resistance on the left. Bulb A is in the top wire, in series with the battery. Beyond A, the circuit splits into two branches joined again at the right. The upper branch holds bulb B. The lower branch holds bulb C in series with a switch S, which is drawn open. All three bulbs are identical and are drawn as circles with a cross.