A sample material with the thermal conductivity $(k_s)$ of $0\mathrm{.}56\frac{W}{m}.K$ has a square shape, of which width $($W$)$ is $25$ cm $.$ Its thickness $($ t $)$ is $2\mathrm{.}5$ cm $.$ The bottom surface is electrically heated. Both the sample and the heater are placed in an insulation so that heat transfer occurs at the top surface. Temperature measurement made at the bottom surface of the sample yields the value of $150C$ for $T_1.$ If the emissivity $()$ of the sample surface is $0\mathrm{.}8,$ what is the electrical power $(P_{\text{e}\text{l}\text{e}\text{c}})?$ The ambient air temperature $(T_{})$ and the surrounding surface temnerature $(T_{\text{c}\text{u}\text{r}\text{r}})$ are both $25C$