-What Is the Net Benefit of the 6th Unit of }

$\begin{array}{cccccc}\text { Level of } & \text { Total } & \text { Total } & \text { Marginal } & \text { Marginal } & \text { Net } \\\text { Activit } & \text { Beneft } & \text { Cost } & \text { Benefit } & \text { Cost } & \text { Benefit }\\\hline0&-&0&xx&xx&0\\1&100&50&-&-&-\\2&-&-&150&0&100\\3&-&-&-&160&115\\4&605&-&-&179&-\\5&-&674&120&-&-\\6&825&-&-&190&-\end{array}$
-What is the net benefit of the 6th unit of the activity?

A) -39
B) 0
C) 45
D) 50
E) none of the above