A student has a number of books that she purchased for her classes: 70% of her books cost under $100, and 30% of her books cost over$100. Of the books that cost under $100, 10% are hardcover and 90% are paperbacks. Of the books that cost more than $100, 80% are hardcover and 20% are paperback. She recently loaned one of her hardcover books to a friend. Now, employ Bayes's Rule to calculate the probability that the book she loaned to her friend cost under $100. Let's assign variables thusly(you may not need to use all the variables): H = The book is a hardcover. P = The book is a paperback. U = Thebook cost under $100. O = Thebook cost over $100.

Now, what would the equation look like?