2 men and 2 women escaped from a yacht just before it sank. The life raft only has space for 3 people. The longest time a man can survive in the water is 3 hours but a woman can survive for 4 hours. After being in the water, they need 10 hours out of the water to recover or they will die immediately. Each time they go back into the water, the time they can survive is reduced by 1 hour.
How long can all 4 people stay alive?