Chapter 2.3, Problem 73E

Labor Costs Suppose that a contractor employs carpenters, bricklayers, and plumbers, working three shifts per day. The number of labor-hours employed in each of the shifts is summarized in the following matrix:

$\begin{array}{l}\frac{\text{Shift}}{\begin{array}{ccc}\text{1}& \text{2}& \text{3}\end{array}}\\ \begin{array}{c}\text{Carpenters}\\ \text{Bricklayers}\\ \text{Plumbers}\end{array}\left[\begin{array}{ccc}50& 20& 10\\ 30& 30& 15\\ 20& 20& 5\end{array}\right]\end{array}$

Labor in shift 1 costs $20 per hour, in shift 2 $30 per hour, and in shift 3 $40 per hour. Use matrix multiplication to compute the dollar amount spent on each type of labor.