4women must cross a bridge over a deep ravine in enemy territory in the middle of the night. the bridge will only old two women at once and it is necessary to carry a lantern while crossing. one of the women requires 25 minutes, one 20 minutes, one 10 minutes and one 5 minutes. each of them can walk slower but not faster. unfortunately they have only one lantern among them. how can they make the crossing if they have only 60 minutes before the bridge is destroyed?