Problem

A wall has two layers

A

and

B

each made of different materials. Both the layers have the same thickness. The thermal conductivity of material

A

is twice of

B

. Under thermal equilibrium the temperature difference across the layer

B

36^{\circ}\text{C}

. The temperature difference across layer

A

is a.

6^{\circ}\text{C}

12^{\circ}\text{C}

18^{\circ}\text{C}

24^{\circ}\text{C}