The main concept is domestic supply and protection levels. I'm pretty sure I didn't do the same paper, but I'm assuming that there was a change in a quota, with the world price (Pw) under the domestic price (Pe), and you had to graph the subsequent change in domestic supply? If the quota increased (i.e. more of the product is permitted to be imported), then this tends to lower prices for consumers as there are cheaper overseas options -> domestic producers are not willing to sell as much for the lower price -> domestic supply curve shifts to the left. The opposite happens if the quota decreases, representing greater protection levels