Suppose that a box contains 1 blue ball and 1 yellow ball. In each round, we take out a ball at random, and then return the ball to the box plus one more ball of the same color. We repeat this process 10 times; there will be 11 balls in the box in the end.

(b)Find the probability that in the end there are 2 blue balls and 9 yellow balls in the box.(Hint:Theevent is the set of outcomes such that the colors of the taken out balls are byy yy, yby yy, yyb yy, and so on. Find the probability of each case and add them up.)

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