Differential Equations

The steady-state temperature distribution $T(x)$ in a uniform slab of thickness $L = 2\text{ m}$ with no internal heat generation satisfying $\frac{d^2 T}{dx^2} = 0$ subject to $T(0) = 100^\circ\text{C}$ and $T(2) = 20^\circ\text{C}$ at the midpoint $x = 1\text{ m}$ is: