Students X, Y and Z are good at logical reasoning. They already know that the drawer has the following 16 playing cards: Heart (♥): A♥、Q♥、4♥ Spade (♠): J♠、8♠、4♠、2♠、7♠、3♠ Club (♣): K♣、Q♣、5♣、4♣、6♣ Diamond (♦): A♦、5♦ Teacher W now picks one card out of these 16 cards from the drawer without X, Y and Z seeing it. Then W tells the rank of this card (i.e., A, 2, 3, 4, 5, 6, 7, 8, J, Q, or K) to Y and the suit of this card (i.e., Heart, Spade, Club, or Diamond) to Z. Then he asks Y and Z whether each of them can infer what this card is just from the partial information they each have. At this point, X hears the following conversation between Y and Z: Y: I don’t know what this card is. Z: I know that you don’t know what this card is. Y: Now I know what this card is. Z: Now I also know what this card is. After hearing the above conversation and thinking for a while, X also knows what this card is. What is this card? Justify your answer. Don't bother googling; the answer isn't online.