Four students, Art, Bob, Cal, and Dan, must be assigned rooms in a college dorm. The dean of housing would like to assign them in stable partnerships, so that no two students would prefer each other to their assigned partners. The students€™ preferences are as follows:

(a) Is there any stable assignment? Explain your answer. (Every student except Dan is the first choice of somebody other than Dan.)
(b) The humorist James Thurber once wrote a book called Is Sex Necessary? In what sense does this example offer an answer to Thurber€™s question?

First Choice Second Choice Third Choice Person Bob Cal Art Art Cal Art Bob Bob Bob Cal Cal