A Wall Has Two Layers of Materials a and B;

Multiple Choice

A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature difference across the wall is 36°C. The temperature difference across the layer A is __________ °C.

A) 6
B) 12
C) 18
D) 24