The differential equation De$)$ d$^2/$dx$^2=0$ is applicable to each section of the composite wall shown in Figure P$3\mathrm{.}2,$ where De$)$ is the thermal con$-$ ductivity. Calculate the nodal temperature values within the wall and evaluate the heat flow through each material. The heat flow is given by q $=$ D$($e$)$ d$/$dx$.$ A unit of surface area is assumed.

Figure P$3.2$

Answer is $2=19\mathrm{.}1$ and $3=-4\mathrm{.}48$