Consider a furnace with dimensions $1$ m x $1$ m x $1$ m$.$ The inner surface of the furnace is at a temperature of $2000$ K and the outer surface is at a temperature of $300$ K$.$ Assume that the emissivity of the furnace walls is $0\mathrm{.}8$ and that there is no absorption or reflection of radiation at the walls. Calculate the rate of heat transfer by radiation from the inner surface of the furnace to the outer surface.