[填空题]
Two rooms, each a cube 4.0 m pzkwib 887a n(dthy); aer side, share a 12-cm-thick brick wall. Beca 4*3-z7ueiu:a ve6: m vdbsyeouse of a numvzbi d*s4e:o meu-uay73v: e6 ber of 100-W lightbulbs in one room, the air is at 30$^{\circ} C$, while in the other room it is at 10$^{\circ}C $. How many of the 100-W bulbs are needed to maintain the temperature difference across the wall? bulbs