Refer to the Information Provided in Table 8 -Refer to Table 8

Refer to the information provided in Table 8.1 below to answer the question(s) that follow.
Table 8.1 $$\begin{array} { l c c c } \text { Produce } & \begin{array} { c } \text { Using } \\\text { Techniques }\end{array} & \begin{array} { c } \text { Units of Variable } \\\text { K }\end{array} & \begin{array} { c } \text { Inputs } \\\text { L }\end{array} \\\hline \text { 1 unit of output } & & & \\& \text { A } & 8 & 8 \\& \text { B } & 4 & 12 \\\text { 2 units of output } & & & \\& \text { A } & 14 & 12 \\& \text { B } & 8 & 20 \\3 \text { units of output } & & & \\& \text { A } & 16 & 12 \\& \text { B } & 12 & 22 \\\hline\end{array}$$
-Refer to Table 8.1. Assume the price of labor (L) is $5 per unit, the price of capital (K) is $10 per unit, and that firms attempt to minimize costs. The marginal cost of producing the third unit of output is

A) $30.
B) $40.
C) $50.
D) indeterminate from this information.