Riddle

2. A group of four people has to cross a bridge. It is dark, and they have to light the path with a
flashlight. No more than two people can cross the bridge simultaneously, and the group has only
one flashlight. It takes a different time for each person in the group to cross the bridge:
? Annie crosses the bridge in 1 minute,
? Bob crosses the bridge in 2 minutes,
? Mito crosses the bridge in 5 minutes,
? Dorothy crosses the bridge in 10 minutes.