1. The problem statement, all variables and given/known data A set of 25 items contains 5 defective items. Items are sampled at random one at a time. What is the probability that the 3rd and 4th defectives occur at the 5th and 6th sample draws if the items are: a.) replaced after each is drawn? b.) not replaced after each is drawn? 2. Relevant equations I s'pose I could use the binomial theorem, but in the section this problem is in - it has not been covered. I really do not know any other useful formulas. 3. The attempt at a solution If I were to define my events, let A: chose non-defective item, and B: chose defective item. The probability, based on the first line of the problem, is P(A) = 0.8. From here, I do not know where to start. Any helpful hints that could get me going? Thank you for all help in advance!