Mary has 4 modern US coins, one each of the common denominations (penny, nickel, dime, and quarter) and 4 modern US bills ($1, $5, $10, and $20). She picks up one of the coins or bills at random, looks at it, declares "Wow! That's my favorite US president!", and puts it in her pocket. John, hearing all the hubbub, comes by, picks up one of the remaining coins or bills at random, looks at it, and declares "Wow! That's my favorite US president!". What is the probability that Mary and John have the same favorite US president?
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