problem set help

1 Problem A person has n keys, of which one will open her door.
1. If she tries the keys at random, discarding those that don’t work, what is the probability that she will open the door on her kth try?
2. What if she does not discard previously tried keys? 2 Problem Consider that a certain part of the memory address space is partitioned into 5 sequential sections. Suppose 5 files of different sizes are randomly written into these section (one file in one section). What is the probability that files will be written in order of their sizes in the sections (the largest in the first section, the second largest in the second section, and so on). 3 Problem Bridge is a card game in which the deck of 52 cards is randomly and equally divided among the 4 players. So each player gets 13 cards….etc please use latex if possible