$[25$ pts$]$ Refractory bricks are used as linings for furnaces, and the generally have low thermal conductivity to minimize heat loss through the furnace walls. Consider a thick furnace wall lined with refractory bricks $(k=1\mathrm{.}0\frac{W}{m}-K$ and $($:$=5\mathrm{.}08{10}^{-7}\frac{m^2}{s}$