$($b$)$ A black body having surface area $0\mathrm{.}035m^2$ is enclosed in an enclosure bounded by $50$ mm thick wall and having surface area $0\mathrm{.}6m^2.$ The inner surface of the enclosure is maintained at $235C$ while the outer surface is at $33C.$ It can be assumed that the innet and the outer surface areas are equal and at steady state conditions.