Solid cylindrical copper rod 0.2m long has one end maintained at temperature 20K, other end blackened and exposed to thermal radiation from surrounding walls at 500K. As the rod is insulated, no energy is lost or gained except at the ends of the rod. When equilibrium is reached, what is the temperature of the blackened end? hint: at 20K, copper's thermal conductivity constant is 1670 W/(mK), so the blackened end will only be slightly over 20K.