In the Table Below,the Capital Stock Is Fixed at 40

Multiple Choice

In the table below,the capital stock is fixed at 40 units,the price of capital is $15 per unit,and the price of labor is $80 per unit. $$\begin{array} { c c } \text { Units of } & \text { Units of } \\\text { Labor } & \text { Output } \\\hline 5 & 40 \\10 & 100 \\15 & 180 \\20 & 220\end{array}$$ How much does the 50th unit of output add to the firm's total cost?

A) $6.67
B) $10
C) $400
D) $600
E) none of the above