An ordinary deck of cards is randomly shuffled and then the cards are exposed one at a time At some time before all the cards have been exposed you must say "next," and if the next card exposed is a spade then you win and if not then you lose For any strategy, show that at the moment you call "next" the conditional probability that you win is equal to the conditional probability that the last card is a spade. Conclude from this that the probability of winning is 1/4 for all strategies