Grass Green Company makes and sells hedge trimmers, which are designed to be safe if used properly. Kayla buys a Grass Green trimmer and lends it to her neighbor Ike. In his garage, Ike is using the trimmer as a prod to dislodge a box from a high shelf when the trimmer suddenly engages. Startled, Ike drops the trimmer, which swings around and cuts his leg. Ike files a product liability suit against Grass Green, on the ground of negligence. On what basis could the manufacturer prevail?