In the city of San Miguel on the island of Cozumel, Mexico, there is a museum with a room devoted to pirates and sailing ships. One of the displays shows a log chip - a small triangular, weighted device used by fifteenth- and sixteenth-century sailors to measure speed. The log chip was tied to a rope that was wound up on a reel. The sailors tied evenly spaced knots in the rope. They would then throw the rope overboard and the weight of the log chip would allow the rope to unreel as the boat moved along. The sailors would allow it to unreel for 30 seconds, timed with a sand hourglass. They would then haul the rope in and count the number of knots that had been reeled out. This number was the speed of the boat in knots (nautical miles per hour). If one nautical mile is 6076.10333 feet (one minute of arc of the earth's circumference), how many feet apart are the knots