#### Answer

4820 ft

#### Work Step by Step

Multiply to find the total inventory for each length, then sum to find the total inventory.
$5\times18\ \ \ \ =\ \ \ \ 90$
$42\times15\ \ =\ \ 630$
$158\times12=1896$
$105\times10=1050$
$79\times8\ \ \ \ =\ \ 632$
$87\times6\ \ \ \ =\underline{\ \ 522}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 4820$