Doesn't it depend on how many people there are? Well, I guess I'll let that be Y. Also, I assume you start at the floor below the first.

(i) The possible values range from 0 to Y

(ii) For 0-

Basically each person has a

chance of not going off at floor 1, and there are X people.

Similarly, for 1 (I'm kind of guessing on this) it's

. ( Or should that be multiplied by Y?)That's a hint, I don't want to do it all, so the rest is yours

(iii)You expect

of the poeple to get off at each floor, so the answer is

Hopefully I got some of these right...