Answer the Question on the Basis of the Following Cost

Answer the question on the basis of the following cost data. $\begin{array} { | c | c | c | } \hline \text { Output } & \text { Average Fixed Cost } & \text { Average Variable Cost } \\\hline 1 & \$ 50.00 & \$ 100.00 \\\hline 2 & 25.00 & 80.00 \\\hline 3 & 16.67 & 66.67 \\\hline 4 & 12.50 & 65.00 \\\hline 5 & 10.00 & 68.00 \\\hline 6 & 8.37 & 73.33 \\\hline 7 & 7.14 & 80.00 \\\hline 8 & 6.25 & 87.50 \\\hline\end{array}$ The marginal cost of the fifth unit of output is

A) $3.
B) $62.
C) $80.
D) $78.