Refer to the Following:
the Amount of Total Output Produced

Refer to the following:
The amount of total output produced from various combinations of labor and capital.

$\begin{array}{cccc} &\text { Units of Capital }\\&& 1 & 2 & 3&4 \\\hline &1 & 50&120&160&180 \\\text {Units }&2 & 110&260&360&390 \\\text {of }&3 & 150&360&510&560\\\text {Labor }&4 & 170&430&630&690 \\&5 & 160&4801&710&790 \\\end{array}$
-If the capital stock is fixed at four units and there are three units of labor, what is the average product of labor?

A) 50
B) 140
C) 157.5
D) 170
E) none of the above