Refer to the Accompanying Table Below A)$20
B)$25
C)$30
D)$40

Refer to the accompanying table below. The average cost of 4 units of this activity is: $$\begin{array} { | c | r r | r | } \hline \text { Units of Activity } & { \text { Tatal Cast } } & { \text { Tatal Benefit } } \\\hline 0 & \$ 0 & \$ 0 \\\hline 1 & \$ 30 & \$ 100 \\\hline 2 & \$ 40 & \$ 160 \\\hline 3 & \$ 60 & \$ 190 \\\hline 4 & \$ 100 & \$ 210 \\\hline 5 & \$150 & \$ 220 \\\hline 6 &\$210& \$ 225 \\\hline\end{array}$$  

A) $20
B) $25
C) $30
D) $40