Calculating optimum thickness of the insulation for composite wall

[onquest]

Homework Statement

A wall is required to be insulated by embedding wood within concrete. the total thickness of the concrete and wood are 10cm and 1 cm respectively and are fixed due to structural constraints. determine the minimum heat leak into the room if the location of the wood can be changed within the concrete. Take K for wood as 0.1w/mk and for concrete 1.0w/mk




Please help.

Homework Equations

thermal resistance

The Attempt at a Solution

I tried solving using thermal resistance concept by equating derivative of the total thermal resistance to 0, but not able to get the answer.

 

[CWatters]

I don't believe they are asking you to find the minimium of an equation (eg I don't think you need to use derivatives). When they use the word minimium I think they are just referring to the fact that their might be other ways for heat to get into the room other than by conduction but these are to be ignored.