Consider a circular furnace that is 0.3 m long and 0.3 m in diameter. the two ends have diffuse, gray surfaces that are maintained at 400 and 500 k with emissivities of 0.4 and 0.5, respectively. the lateral surface is also diffuse and gray with an emissivity of 0.8 and a temperature of 800 k. determine the net radiative heat transfer from each of the surfaces. consider two very large metal parallel plates.