To determine the year when the price per bag of cookies was $4, you would look for the point on the graph where the price (y-axis) intersects with the value of $4.
If the graph shows a curve representing the price of cookies over time starting from 2007, you would find the corresponding x-coordinate (time in years since 2007) where the y-value is $4.
For example, if you find that the x-coordinate is 3, that would indicate the year 2010 (since 2007 + 3 = 2010).
Without the actual graph, I can't specify the exact year, but you should follow this approach to find the intersection point for the price of $4.