A person visits a certain Web site according to a Poisson process with rate λ per day. The site in question contains a main page and an internal link. The probability that the person visits only the main page is equal to ¾ (independently from one visit to another) Moreover, when she clicks on the internal link (at most once per visit), the probability that she will return (afterward) to the main page is equal to 1/2. We define the states
0: the person is not visiting the site in question
1: the person is visiting the main page (coming from outside the site)
2: the person is visiting the internal link
3: the person is visiting the main page, after having visited the link
