Table 7-2 Table 7-2 Above Shows Keira's Utility from Soup and Sandwiches

Multiple Choice

Table 7-2
$$\begin{array} { | c | c | c | c | } \hline \begin{array} { c } \text { Quantity of } \\\text { Soup (cups) }\end{array} & \text { Total Utility } & \begin{array} { c } \text { Quantity of } \\\text { Sandwiches }\end{array} & \text { Total Utility } \\\hline 1 & 40 & 1 & 45 \\\hline 2 & 60 & 2 & 75 \\\hline 3 & 72 & 3 & 102 \\\hline 4 & 82 & 4 & 120 \\\hline 5 & 88 & 5 & 135 \\\hline 6 & 90 & 6 & 145 \\\hline\end{array}$$
Table 7-2 above shows Keira's utility from soup and sandwiches.The price of soup is $2 per cup and the price of a sandwich is $3.Keira has $18 to spend on these two goods.
-Refer to Table 7-2.What is Keira's marginal utility per dollar spent on the third cup of soup?

A) 72 units of utility
B) 36 units of utility
C) 12 units of utility
D) 6 units of utility