Table 6-D
the Table Below Shows How Total Cost Varies

Table 6-D
The table below shows how total cost varies with output in a factory producing watches:
$$\begin{array} { c c } \begin{array} { c } \text { Output } \\\text { (Per Week) }\end{array} & \begin{array} { c } \text { Tatal Cost } \\\text { (Dollars) }\end{array} \\\hline 0 & \$ 50 \\1 & \$ 60 \\2 & \$ 65 \\3 & \$ 69 \\4 & \$ 72 \\5 & \$ 95 \\6 & \$ 120\end{array}$$
-Refer to Table 6-D.The marginal cost of producing a third watch equals:

A) $50.
B) $69.
C) $5.
D) $4.
E) none of the above.