A certain material 2.5 cm thick, with a cross-sectional area of 0.1 m2, has one side maintained

Question:

A certain material 2.5 cm thick, with a cross-sectional area of 0.1 m2, has one side maintained at 35ºC and the other at 95ºC. The temperature at the center plane of the material is 62ºC, and the heat flow through the material is 1 kW. Obtain an expression for the thermal conductivity of the material as a function of temperature.