-What Is the Marginal Cost of the 1^st Unit of }

$\begin{array}{cccccc}\text { Level of } & \text { Total } & \text { Total } & \text { Marginal } & \text { Marginal } & \text { Net } \\\text { Activit } & \text { Beneft } & \text { Cost } & \text { Benefit } & \text { Cost } & \text { Benefit }\\\hline0&-&0&xx&xx&0\\1&200&30&-&-&-\\2&-&-&100&-&230\\3&-&-&-&50&270\\4&450&-&-&65&-\\5&-&255&30&-&-\\6&500&-&-&75&-\end{array}$
-What is the marginal cost of the 1^st unit of the activity?

A) 0
B) 5
C) 10
D) 15
E) none of the above