Refer to Table 21 What Is the Unit Labor Cost in Table 21

Refer to Table 21.3 below: Table 21.3
$$\begin{array} { | c | r | r | } \hline \text { Units of Lubor } & \text { Units of Output } & \text { MPP } \\\hline 0 &0& \\\hline 1 & &30 \\\hline 2 & 66& \\\hline 3 &&30 \\\hline 4 & 116 \\\hline\end{array}$$
What is the unit labor cost in Table 21.3 for the second unit of labor if the MPP represents daily output and the wage rate is $72 per day?

A) $0.50 per unit of output.
B) $2.00 per unit of output.
C) $36.00 per unit of output.
D) $72.00 per unit of output.