Refer to the Above Table

$$\begin{array} { | c | c | c | } \hline \text { Price Per Unit } & \text { Quantity Demanded Per Year } & \text { Quantity Supplied Per Year } \\\hline \$ 5 & 2,000 & 0 \\\hline 10 & 1,800 & 300 \\\hline 15 & 1,600 & 600 \\\hline 20 & 1,400 & 900 \\\hline 25 & 1,200 & 1,200 \\\hline 30 & 1,000 & 1,500 \\\hline\end{array}$$ Refer to the above table. A surplus of 500 units will occur when the price is

A) $10 per unit.
B) $15 per unit.
C) $20 per unit.
D) $30 per unit.