$2\mathrm{.}5$ Assume steady$-$state, one$-$dimensional heat conduction

through the symmetric shape shown.

Assuming that there is no internal heat generation,

derive an expression for the thermal conductivity $k(x)$

for these conditions: $A(x)=(1-x),T(x)=300$

$(1-2x-x^3),$ and $q=6000W,$ where $A$ is in square

meters, $T$ in kelvins, and $x$ in meters.