I run a retail store that hires extra cashiers for the holiday rush. Each year, we sign six-week contracts with short-term employees, under which we train them for two weeks before Thanksgiving and then employ them as cashiers for all of December at a pre-agreed wage.

Consider the following two scenarios:

• You agree to the contract. The day after Thanksgiving, I've already invested time and money in training you, and don't have time to train a replacement; you suddenly realize you're in a strong bargaining position, and threaten to quit unless I raise your salary.

• You agree to the contract. Watching you interact with customers and other employees during training, I realize you're better suited to be a store manager than a cashier. The work is harder - you wouldn't agree to do it for the same wage - but your additional value to me as a manager is much greater than the additional cost (effort) to you. We rewrite the contract to make you a manager and pay you more.

(a) Give an economic argument why the renegotiated contract should be enforced in the second scenario, while the original contract should be enforced in the first.

(b) Would either renegotiated contract be enforced under the Bargain Theory of contracts?