The plaintiff brings this cause of action against a manufacturer for the loss of his leg below the hip. The leg was lost when caught in the gears of a screw auger machine sold and installed by the defendant. Shortly before the accident, the plaintiff's co-employees had removed a covering panel from the machine by use of sledgehammers and crowbars in order to do repair work.

When finished with their repairs, they replaced the panel with a single piece of cardboard instead of restoring the equipment to its original condition.

The plaintiff stepped on the cardboard in the course of his work and fell, catching his leg in the moving parts. Explain what causes of action the plaintiff may have against the defendant and what defenses the defendant could raise.