Leslie is buying potatoes at a store. This graph shows the relationship between the number of pounds of potatoes she buys and the total cost. The picture shows a line graph, titled Cost of Potatoes. The horizontal axis is labeled, Weight of Potatoes in pounds. The values shown on the horizontal axis are zero through five. The vertical axis is labeled Cost in Dollars. The values shown on the vertical axis are zero through five. The line on the graph starts at zero pounds and zero dollars. The line moves in the upward direction. It passes through the point two pounds and one and one-half dollars. It also passes through the point four pounds and three dollars.

Based on the graph, what is the unit cost, in dollars, of the potatoes?