Pauline Brown was shot and seriously injured by an unknown assailant in the parking lot of National Supermarkets. Pauline and George Brown brought a negligence action against National; Sentry Security Agency; and T. G. Watkins, a security guard and Sentry employee. The Browns maintained that the defendants have a legal duty to protect National’s customers, both in the store and in the parking lot, and that this duty was breached. The defendants denied this allegation. What will the Browns have to prove to prevail? Explain.