Given a 50 card deck with cards numbered from 1 through 10 in each of 5 suits, how many 5 card hands are there that include exactly one pair of two cards that have the same numeric value?

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https://math.stackexchange.com/questions/1374692/given-a-50-card-deck-with-cards-numbered-from-1-through-10-in-each-of-5-suits-h