There are $3$ married couples who need to cross a river. They have a boat that can hold no more than two people at a time. To complicate matters, all the husbands are jealous and will not agree on any crossing procedure that would put a wife on the same bank of the river with another woman$$s husband without the wife$$s husband being there too, even if there are other people on the same bank. Draw the state

space diagram that shows a feasible boat trip such that all couples cross the river.