At high tide, the tip of the prow of a boat was level with the surface of a dock. The owner fastened a rope to the top of a three-foot pole on the dock, and fastened the other end to the tip of the prow. There was exactly 25 feet of rope between these two points. When the owner return at low tide, the rope was pulled taut and made an angle of 35° with the pole. Which of the following expressions gives the best approximation of the difference in water height between high and low tide?