A man on a dock is pulling in a boat by means of a rope attached to the bow of the boat at a point that is 1 ft above water level. The rope goes from the bow of the boat to a pulley located at the edge of the dock 9 ft above water level. If he pulls in the rope at a rate of 2 ft/sec, how fast (in feet per second) is the boat approaching the dock when the point of attachment is 19 ft from the dock?