AMC 10 2014b Problem 6

Orvin went to the store with just enough money to buy $30$ balloons. When he arrived, he discovered that the store had a special sale on balloons: buy $1$ balloon at the regular price and get a second at $\frac{1}{3}$ off the regular price. What is the greatest number of balloons Orvin could buy? $\textbf {(A) } 33 \textbf {(B) } 34 \textbf {(C) } 36 \textbf {(D) } 38 \textbf {(E) } 39$