The Table Below Shows How the Marginal Benefit of Car

The table below shows how the marginal benefit of car washes varies for Carol with the number purchased per month. $$\begin{array} { | c | c | } \hline \text { Car washes per month } & \begin{array} { c } \text { Marginal benefit of purchasing an additimal car } \\\text { wash }\end{array} \\\hline 1 & \$ 6.00 \\\hline 2 & \$ 5.00 \\\hline 3 & \$ 4.00 \\\hline 4 & \$ 3.00 \\\hline 5 & \$ 2.00 \\\hline\end{array}$$ The price of each car wash is reduced from $2.99 to $1.99. Assuming that the price of a car wash accurately reflects the marginal cost to Carol and that she is rational, she will increase the number of car washes purchased per month from:

A) one to two.
B) two to three.
C) three to four.
D) four to five.