"U2" has a concert that starts in 17 minutes and they must all cross a bridge to get there. All four men begin on the same side of the bridge. You must help them cross to the other side. It is night. There is one flashlight. A maximum of two people cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them. The flashlight must be walked back and forth, it cannot be thrown, etc. Each band member walks at a different speed. A pair must walk together at the rate of the slower man's pace.
Bono - 1 minute to cross  Edge - 2 minutes to cross
Adam - 5 minutes to cross Larry - 10 minutes to cross
For example - If Bono and Larry walk across first, 10 minutes have elapsed when
they get to the other side of the bridge. If Larry then returns with the flashlight, a
total of 20 minutes has passed, and the band has failed to get to the concert on
time.