A local supermarket has three checkout counters. Two customers arrive at the counters at different times when the counters are serving no other customers. Each customer chooses a counter at random,...

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Extracted text: A local supermarket has three checkout counters. Two customers arrive at the counters at different times when the counters are serving no other customers. Each customer chooses a counter at random, independently of the other. Let Y1 denote the umber of customers who choose counter 1 and Y2, the number who select counter 2. Find the joint probability distribution function for Y1 and Y2.