After your first semester of college is over, you discover that the math department has changed textbooks (again) so the bookstore won't buy back your nearly-new book. You and your friend Amber decide to get creative. You go to the roof of a twelve-story building and look over the edge to the reflecting pool 160 feet below. You drop your book over the edge at the same instant that Amber chucks her book straight down at 48 ft/s. By how many seconds does her book beat yours into the water?