Then repeat that process ten times. Thus the outcome space is a set of ten pairs of letters.
Actually this a simple binomial distribution.
: the probability of two A's.
: the probability of two B's
: the probability of two C's.
Thus the probability getting two of a kind on any one turn is .
Let stand for the probability of getting matching pairs in ten turns.
That is for box I.
For box II. change 10 to 5.
Did I read the question correctly?