An electric heater is used in a room of total wall area 137 m 2 to maintain a temperature of 20°C inside it when outside temperature is –10°C. The walls have three different layers of materials. The innermost layer is of wood of thickness 2.5 cm, the middle layer is of cement of thickness 1.0 cm and the outermost layer is of brick of thickness 25 cm. Find the power of the electric heater :-(Assume that there is no heat loss through the floor and the ceiling. The thermal conductivities of wood, cement and brick are 0.125, 1.5 and 1.0 W/m C° respectively).