(a)The question is rather misleading. It can be interpreted in two different scenarios: (i) A 240V circuit supplying two lamps expending 60W and 100W power respectively. In this case, the 100W lamp will be brighter with a resistance =11.875?, 60W with R=7.125?. (ii) Two 240V lamps rated at 60W and 100W respectively are connected in series. In this case, the result will be as Hamid has given. Both rooms will have a 15W lighting outpu, total for two rooms is 30W. (b) Answer to Hamid’s question, based on (ii) above, use maximum power transfer principle, assume the source is an ideal source, add a 150W in series with 100W in room B. (c) Bill, the bulbs will not burn out unless they were at a much lower voltage rating (i.e., 50V rated). Since they are connected in series, they cannot burn out separately. They will need to be burnt out simultaneously.