Puzzel : There are 4 persons (A,B,C, and D) who wants to cross a bridge in night . A takes 1 minute to cross the bridge. B takes 2 minutes to cross the bridge. C takes 5 minute to cross the bridge. D takes 10 minutes to cross the bridge. There is only one torch with them and the bridge cannot be crossed without the torch . There cannot be more than 2 persons on the bridge at any time, and when 2 people cross the bridge together , they must move at the slower person. What is the minimum tie required to cross the bridge.