Regina has a shelf that is eight feet off the ground. When she was younger she used the shelf for storage, and her mom would help her use a ladder to reach things on it occasionally. Now she wants to use the shelf to hold her textbooks that she needs to use every day. She needs to be able to do this by herself without using the ladder. Regina needs to design a tool to help her reach the books ont he shelf easily and safely. She wants to use materials she finds around the house to make the tool. List one criterion and one constraint for the tool she is designing.