Jane is walking her dog, spot. She sees her friend, Richard, walking toward her along the same long, straight road. Both Richard and Jane are walking at 3 mph. When Richard and Jane are 600 feet apart, Spot runs from Richard to Jane, turns and runs back to Richard, and then back and forth between them at a constant speed of 8 mph. Richard and Jane both continue walking toward each other at a constant 3 mph. Neglecting the time lost each time Spot reverses direction, how far has Spot run in the time it takes Richard and Jane to meet?