When I borrow a book from the city library, I usually try to return it after one week. Depending on the length of the book and my free time, there is a 30% chance that I may keep it for another week. If I have had the book for two weeks, there is a 10% chance that I’ll keep it for an additional week. Under no condition do I keep it for more than three weeks. (a) Express the situation as a Markov chain (b) Determine the average number of weeks I keep a book before returning it to the library.