Problem 11
Alice, Bob, Charles, and Denise are walking through the woods late at night when they come upon an old, rickety bridge. The group determines that the bridge can safely hold at most two people simultaneously. They also decide that it is unsafe to cross the bridge without the aid of a flashlight, which they have only one of. Alice can cross the bridge alone in 1 minute, Bob can cross alone in 2 minutes, Charles can cross alone in 4 minutes, and Denise can cross alone in 5 minutes. Two of them may cross at once if one of the two has the flashlight, but they must travel at the speed of the slower person. In order for everyone to get to the other side, someone must bring the flashlight back after each crossing. What is the fastest time in which all four can make it across the bridge? How is this accomplished?
****UPDATE****
All 4 people start on the same side of the bridge and must end up on the opposite side. If a person crosses the bridge and then comes back, he or she must then cross again to make it to the other side.
