2.7 The insulated box shown in the figure is designed to keep the air trapped in it at a high temperature, T = 50C. The outside temperature is T, = 10C. To keep the temperature of the trapped air constant, the heat transfer that leaks through the insulation, q, is made up by an electrical resistance heater placed in the center of the box. Calculate the electrical power dissipated in the heater. The dimensions of the internal (air) space are x = 1 m, y = 0.4 m, and z = 0.3 m. The insulating wall consists of a 10-cm-thick layer of fiberglass sandwiched be- tween two plywood sheets. The plywood sheet is 1 cm thick. The heat transfer coefficients on the internal and external surfaces of the wall are, respectively, h = 5 W/m K and h = 15 W/m.K. Figure P2.7 Insulation Plywood sheets Fiberglass layer