Bob, Peter, and Chris travel together. Peter and Chris are good hikers; each walks p miles per hour. Bob has a bad foot and drives a small car in which two people can ride, but not three; the car covers c miles per hour. The three friend adopted the following scheme: They start together. Chris rides in the car with Bob and Peter walks. After a while, Bob drops Chris who walks on; Bob returns to pick up Peter, and then Bob and Peter ride in the car until they overtake Chris. At this point, they change. Chris rides and Peter walks just as they started and the whole procedure is repeated as often as necessary. How far did they go after an hour?