Typical C trap. Once you know the slowest runner's speed, you know how much time it will take all 3 to finish.
There are three sprinters on a racetrack. How much time will it take all three to finish an 800 meters race?
(1) The first runner can run the fastest, he runs at a 110% of the slowest runner.
(2) The slowest runner runs at a constant speed of 7 meters per second.