1. The problem asks to identify external forces acting on different systems and their directions. 2. For part (b), we consider forces outside each system acting on it: - Book on hand: force is downward (gravity and book's weight act down on hand). - Hand on book: force is upward (hand supports the book). - Floor on book: NA (floor does not act on book directly in this context). - Earth on book: NA (earth's gravity acts on book but is considered internal or not external here). 3. For part (c), forces acting on the hand are: - Book on hand (downward force from book's weight). - Hand on book (reaction force upward from hand to book). - Floor on hand and Earth on hand are not acting forces on the hand in this scenario. 4. Summary: - External forces on hand: book on hand (down), hand on book (up). - External forces on book: hand on book (up), book on hand (down). This analysis follows Newton's third law and the concept of action-reaction forces.