Table 11
Table $1.1$ Sergio Tutors Fellow Students For $\$ 10$

Table 1.1
Table $1.1$
$\begin{array}{|l|l|}\hline \text { Hours } & \text { Revenue } \\\hline 1 & \$ 10 \\\hline 2 & \$ 20 \\\hline 3 & \$ 30 \\\hline 4 & \$ 40 \\\hline 5 & \$ 50 \\\hline\end{array}$
Sergio tutors fellow students for $\$ 10$ an hour.
-Refer to Table 1.1. Sergio hires an assistant for $5 per hour. What is his marginal cost if he tutors 5 hours a week and also pays his assistant?

A) $25
B) $20
C) $15
D) $10
E) $5