A set of four 3x5 cards is dealt on a table
as shown above. Each card has a letter
on one side and a number on the other.
   The dealer proposes that these 4 cards satisfy the rule:
   “If there is a vowel on one side of the card,
then there is an odd number on the other.”
   What is the smallest number of cards you have to turn
over to be sure the rule is satisfied?  Which ones?