A cube of wood and a cube of concrete, each 0.17 m on a side, are placed side by side. One of the long faces of the rectangular prism formed by the two cubes is held at 17°C, and the opposite long face is held at 32°C. What is the total rate of heat transfer through the cubes?

Answer 1

If you examine the interface of the two cubes, you will find no heat flow from cube to cube..Why?

So, find the heat flow on each cube, and add them.