You are fishing in a boat anchored in a bay. You notice that the current is in the eastern direction with small wave crests that are 15 meters apart, and they are gently rocking the boat once every 5 seconds. You decide to lift the anchor and begin trolling slowly to the west at 2.0 meters/second. In 1-2 sentences, explain the strategy for calculating how often the wave crests will rock the boat in this situation based on your investigation. (2 points)