Thermodynamics Part 4

Two plates A and B have thermal conductivities 84Wm−1K−1 and 126Wm−1K−1 respectively. They have same surface area and same thickness. They are placed in contact along their surfaces. If the temperatures of the outer surfaces of A and B are kept at 100∘C and 0∘C respectively, then the temperature of the surface of contact in steady state is ______ ‌∘C.