Please explain this for me

Suppose you went trick-or-treating (as an adult) and were able to nab N total candies, K of which are kit-kats. The following two parts should be treated separately - only the information above is common to both. = (a) Your responsible parent says you can only eat n of them tonight. You reach in and randomly grab n of them. Let X be the number of kit-kats you grabbed. What is P(X = k) for valid values of k? (b) You eat candies one at a time, randomly without looking into the bag, and decide to stop when you've eaten k kit-kats. Let Y be the total number of candies you ate, up to and including the time you ate your k-th kit-kat. What is P(Y = n) for valid values of - n? - =