Detailed solution please

[5] 7. Bonus (not required) A game is played as follows. In a group of N people, one person has a secret word and decides to tell it to one other person, chosen at random. This new person, tells one other randomly chosen person. This process continues, each one sharing the secret word with one other, until someone 2 has been told ist exactly twice. At this point the game ends and X =number of people who have beeen told the secret word. (a) Find the probability function of X. (b) Find the expected value of X when N = 10. (c) Find an approximation of the c.d.f of the random variable Y = 4 that applies when N - co