Puzzle From Microsoft.

Provided by Alec Li

Dear Lighters
We want to try something new this time. How about a puzzle for you to solve. I copied from my friend. It is as follows:

This is a test given to perspective employees of Microsoft. The band U2 has a concert that starts in 17 minutes, they must all cross a bridge to get there. You must help them cross to the other side.

There is one flashlight. A maximum of two people can cross at one time . Any party who crosses, either one or two 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. Carrying anyone across is not permitted. A pair must walk 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 walked across, 10 minutes has elapsed when they get to the other side of the bridge. If Larry then returned with the flashlight, a total of 20 minutes has passed and you have failed your mission.

Note: There are no tricks involved!! This was given to me by a math lover

P.S. Microsoft gives applicants 5 minutes to solve the problem. I know the answer and if you give up, I will let you know.

Alec Li