You have 26 cards, labeled with the letters A-Z. The deck is shuffled randomly. You draw cards without replacement. (a) Let I be the number of letters we needed to draw to have seen both A and B. For example, if the 3rd letter is A and the 5th letter is B, then L = 5. What is the PMF of L? (b) Given that we have drawn k many cards already (for some k 0,..., 24) and neither A nor B have yet appeared, what's the probability that these two letters will be drawn consecutively (either AB or BA)? =