Elementary Technical Mathematics

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