(a) The number of atoms of a strange element on Earth per hour is the average of the number of atoms in two previous hours. Assume that there were 100,000 atoms in hour 1 and 300,000 atoms in hour 2. Construct a recurrence relation for the number of atoms in hour n. State two initial conditions.
(b) Suppose that in a bookshop every month fifty new copies of a book are added for each book that was present the previous month, and that all books that are 2 months old are removed. The bookshop starts with five new books. Set up a recurrence relation for the number of books present after n months. State two initial conditions.