This is the actual test given by Microsoft to prospective employees.  It's
 solvable without any tricks.  See how you do.  

 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 across to the other side.

 It is night.  There is one flashlight.  

 A maximum of two people can cross at one time.  

 Any party who crosses, either 1 or 2 people, must have the flashlight with

 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 have passed and you have failed.  

 Notes: There is no trick here.  It is the simple movement of resources in the
 appropriate order.  There are two known answers to this problem.  This is
 based on a question Microsoft gives to all prospective employees.

 They expect you to answer in under 5 minutes...