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Because of limited funds, 5 research centers are to be chosen out of 13 suitable ones for a study on heart disease. If the selection is made at random, what is the probability that 5 particular research centers will be chosen? Let the sample space S be the set of ways 5 research centers that can be chosen out of 13 suitable ones. The number of elements in the sample space S is n(S)= (Type a whole number.) The probability is (Type an integer or a simplified fraction.)