Table 6-B -Refer to Table 6-B

Table 6-B
$$\begin{array} { | c | c | c | c | } \hline \text { Units af Output } & \begin{array} { c } \text { Variable Cast } \\\text { (dallars) }\end{array} & \text { Tatal Cast (dollars) } & \begin{array} { c } \text { Marginal Cast } \\\text { (dallars) }\end{array} \\\hline0 & 0& 40 & \\\hline 1 & 30 & 70 & 30 \\\hline 2 & 50 & 90 & 20 \\\hline 3 & 60 & 100 & 10 \\\hline 4 & 80 & 120 & 20 \\\hline 5 & 105 & 145 & 25 \\\hline 6 & 150 & 190 & 45 \\\hline\end{array}$$
-Refer to Table 6-B.How much are average fixed costs (in dollars) at 4 units of output?

A) 10
B) 20
C) 30
D) 40
E) There is insufficient information to determine the average fixed cost at that production level.