4 men stand at the entrance of a dark tunnel. Man A needs 10 minutes to pass through the tunnel, man B needs 5 minutes, man C needs 2 minutes and man D needs 1 minute. There is only one torch, that may be used from anyone that passes through the tunnel. Additionaly, at most 2 men can pass through at the same time using the existing torch.
Determine the smallest possible time the four men need to reach the exit of the tunnel. combinatoricsalgebraminimum