Answer:
a. promptly notify ABC of the intent to cure.
Explanation:
After making a mistake, the first thing you need to do is to communicate with the buyers and try to make amends. You can explain the reason for the mistake and hope that the buyer will be understanding enough to allow you to fix the mistake. This might minimize your lost because of this mistake.
Keep in mind that at this point, the buyer have the full right to cancel the order and abandon his part of the contract.
If the buyer decided to do that, Big Board Games need to accept that decision professionally and prevent similar mistakes from occurring in the future.