4.19 Virus propagation We start with a network of three computers. Unbeknownst to us, two of the computers are infected with a hidden virus and the other is not. A sequence of new uninfected computers now join the network, one at a time. Each new computer joins the existing network by attaching itself to a random computer in the network {(all computers in the network are equally likely attachment points). If the new computer attaches itself to an infected computer, then it immediately becomes infected with the virus; otherwise the new computer does not get the virus. At the point where the network consists of & total computers, what is the expected fraction of these that is infected? Assume > 3