The Marginal Cost Between 20 and 30 Units of Output

Multiple Choice

$$\begin{array}{l}\begin{array} { | l | r | r | r | r | } \hline \text { Output (units per day) } & 0 & 10 & 20 & 30 \\\hline \text { Total cost (dollars per day) } & \$ 40 & \$ 54 & \$ 62 & \$ 80 \\\hline\end{array}\\\text { Table } 21.2\end{array}$$ The marginal cost between 20 and 30 units of output in Table 21.2 is

A) $1.60.
B) $4.00.
C) $1.80.
D) $18.00.