In the Table Below,what Are the Marginal Costs of the Fourth

Multiple Choice

In the table below,what are the marginal costs of the fourth unit of output? $$\begin{array} { c c } \begin{array} { c } \text { Total } \\\text { Output }\end{array} & \begin{array} { c } \text { Total } \\\text { Variable Cost }\end{array} \\\hline 0 & \$ 0 \\1 & \$ 10,000 \\2 & \$ 20,000 \\3 & \$ 30,000 \\4 & \$ 40,000 \\\hline\end{array}$$

A) $10,000
B) $20,000
C) $30,000
D) $40,000