Suppose Sarah Owns a Small Company That Makes Wedding Cakes

Suppose Sarah owns a small company that makes wedding cakes. The table below shows how Sarah's total cost varies depending on the number of wedding cakes she makes each day. $$\begin{array} { | c | c | } \hline \begin{array} { c } \text { Number of } \\\text { Cakes Per Day }\end{array} & \begin{array} { c } \text { Total Cost } \\\text { Per Day }\end{array} \\\hline 0 & \$ 100 \\\hline 1 & \$ 180 \\\hline 2 & \$ 220 \\\hline 3 & \$ 300 \\\hline 4 & \$ 400 \\\hline 5 & \$ 520 \\\hline 6 & \$ 660 \\\hline\end{array}$$ The marginal cost if the 4^th wedding cake per day is ______.

A) $100
B) $120
C) $300
D) $400