Two boats start together and race across a 80-km-wide lake and back. Boat A goes across at 80 km/h and returns at 80 km/h. Boat B goes across at 40 km/h, and its crew, realizing how far behind it is getting, returns at 120 km/h. Turnaround times are negligible, and the boat that completes the round trip first wins. a. Which boat knows?
b. By how much?