where $x$ is the distance away from the surface being heated and $T$ is

the temperature. Compute the temperature gradient $d\frac{T}{d}x$ and the sec$-$

ond derivative $d^2\frac{T}{d}{x}^2$ at $x=0.$ The heat transfer rate is proportional

to the temperature gradient at $x=0.$ The second derivative is related

to energy lost or gained by radiative transport. Employ forward dif$-$

ferences to $O[(x{)}^2]$ and reduce $x$ to obtain numerical results that are

largely independent of the value of $x$ chosen.