Chapter 5.6, Problem 2TU

According to Doyle log rule, the length $L$ in feet, of a log that will produce 100 boards feet of lumber is given by,

$L=\frac{1600}{{\left(D-4\right)}^2}$

Here $D$ is the diameter, in inches, of the log measures at the small end. The formula is valid for logs whose diameters are greater than 4 inches. Identify the pole and explain in practical terms the meaning of pole.