From the Information Below,determine the Contribution Margin Per Unit of Limiting

Multiple Choice

From the information below,determine the contribution margin per unit of limiting factor (labour hours) .
$\begin{array}{|l|r|}\hline \text {Selling price per unit} & \$ 150 \\\hline \text {Variable costs per unit }& \$ 120 \\\hline\text { Labour hours per unit }&\text { 3 hours} \\\hline\end{array}$

A) $3
B) $40
C) $10
D) $30