Please show all the work

(20) An author has written two drafts of a book. In each draft, the number of errors per page is a Poisson random variable. The mean number of errors per page is 3.2 in the first draft, and 1.9 in the second draft. The editor has both drafts but can't tell which is which, so they randomly select one of the drafts, and open it to a random page. If this page has 2 errors on it, draw a tree diagram for this experiment, and find the probability that the editor selected the second draft