Probability & Stochastic ProcQ3

[15 marks] Chain letter emails are those that, in the body or subject of the message, ask the recipient to forward the email on to multiple people. Many chain letter emails are hoaxes and are often considered to be a security and privacy risk. Suppose that the chain starts with the email being anonymously sent to X0 = 1 individual, and that, independently of anything else, each individual receiving the email will forward it to Y 2 Y1 + Yz other people, where Y1 and Y2 are independent and for j = 1, 2: IP(Y}=IC)=(1p)kp (k=0,1,2,...), for somep 6 (0,1). (Hint: for |:r|