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A machinę manufaciurcs cards. It is programmed to print at random, on the front of each card, a 4 or a 6. On the back of each card, it prints a letter:

-    when there is a 4, it prints either an A or an E at random

-    when there is a 6, it prints an E.

One day, Mr. Bianchi, the person in charge, realizes that the machinę has produced some cards it should not have printed. On the back of the cards with a 6, the machinę has not always printed an E; sometimcs it has printed an A instead of an E. Mr. Bianchi fixes the machinę, examines the newly printed cards and says, “don’t worry, the machinę works fine.”

Indicate which of these cards you necd to tum ovcr in order to judge whether the following rulc is truć:

If a card has a 6 on the front, it has an E on the back.