Answer
$L=14$ in
Work Step by Step
We know that the volume of a rectangular box is given by:
$Volume=Length*Width*Height$
$V=LWH$
We can solve this for length:
$L=\frac{V}{WH}$
We plug in $V=238$, $W=8.5$, and $H=2$ (from Exercise 47):
$L=\frac{238}{2*8.5}$
$L=14$ in