Answer the Question on the Basis of the Accompanying Table $$\begin{array} { c r } \text { Output } & \text { ATC } \\\hline 1 & \$ 40 \\2 & 27 \\3 & 29 \\4 & 31 \\5 & 38\end{array}$$

Answer the question on the basis of the accompanying table that shows average total costs (ATC) for a manufacturing firm whose total fixed costs are $10: $$\begin{array} { c r } \text { Output } & \text { ATC } \\\hline 1 & \$ 40 \\2 & 27 \\3 & 29 \\4 & 31 \\5 & 38\end{array}$$ Refer to the data.The average variable cost of 4 units of output is:

A) $33.50.
B) $28.50.
C) $19.00.
D) $21.00.