For the Output Levels in Table 21

Multiple Choice

$\begin{array}{l}\begin{array} { | l | r | r | r | r | } \hline \text { Output (units per day) } & 0 & 10 & 20 & 30 \\\hline \text { Total cost (dollars per day) } & \$ 40 & \$ 54 & \$ 62 & \$ 80 \\\hline\end{array}\\\text { Table } 21.2\end{array}$ For the output levels in Table 21.2, the minimum of the average variable cost curve occurs at a production rate of

A) Zero units per day.
B) 10 units per day.
C) 20 units per day.
D) 30 units per day.