I Contradict You!
There are five two-sided cards lying on a table. Each card contains a letter on one side and a positive integer on the other. Two cards show the letters \(A\) and \(B\). The other three cards show the numbers \(2, 4, 6\). The back sides of these cards are not visible.
Alice says, "If a card has an odd number on one side, then the other side must have a vowel."
Bob proved Alice wrong by turning over one card. Which card is it?