5. Delta Company makes and sells table saws, which are designed to be safe if used properly. Erin buys a Delta saw and lends it to her neighbor Frank. To reach a toolbox on a high shelf in his garage, Frank props the saw at an angle against a cabinet and climbs onto the saw. Frank loses his footing, slips off the saw, falls on the blade, and is injured. He files a product liability suit against Delta, on the ground of negligence. What must Frank show to establish his case? On what basis could Delta prevail?