The Thermal Conductivity of a Certain Concrete Is 0 $\mathrm { W } / \mathrm { m } , \mathrm { K }$

Multiple Choice

The thermal conductivity of a certain concrete is 0.80 $\mathrm { W } / \mathrm { m } , \mathrm { K }$ and the thermal conductivity of a certain wood is 0.10 $\mathrm { W } / \mathrm { m } \cdot \mathrm { K }$ How thick would a solid concrete wall have to be in order to have the same rate of heat flow through it as an 8.0-cm thick wall made of solid wood? Both walls have the same surface area and the same temperature difference across their faces.

A) 53 cm
B) 64 cm
C) 85 cm
D) 71 cm