A stereo receiver/amplifier is enclosed in a thin metallic case for which the top, horizontal surface is 0.5 m x 0.5 m on a side. The surface, which is not vented, has an emissivity of ε = 0.8 and is exposed to quiescent ambient air and large surroundings for which T∞ = Tsur = 25°C. For surface temperatures in the range 50 < Ts < 75°C, compute and plot the total heat rate from the surface, as well as the contributions due to convection and radiation.