Some court cases applicable on the principle of unilateral contract

Awater pipe bursts, flooding a general business company (gbc) utility room and tripping the circuit breakers on a panel in the room. gbc contacts hal, a licensed electrician with ten years of experience, to investigate the damage and turn the breakers "on." hal attempts to turn on one of the breakers without testing for short circuits, which he knows should be done. hal is electrocuted, and files a suit against gbc for damages, al­leging negligence. how might gbc defend itself?