Many Now & Z/Yen readers will have debated at length the infamous Monty Hall problem, popularised last summer by Z/Yen on the Lady Daphne and obscurely written up by The Economist last month. Contrary to previous published advice, Michael Mainelli has now proved that you should stick in the three door problem. We summarise:

S n=1….¥ (r s )(nr s ) where n<=3 q.e.d. This proof has implications for decision theory, game theory, chaos theory and quantum theory. Michael is now trying to work out how to make money out of it. A fool proof solution is available from Z/Yen on request.