(b) That's wrong. This question involves remedies for breach of contract; and in particular for a breach of warranty.
A warranty is defined as a term of the contract that is of less importance than a condition. A breach of that warranty does not justify rejecting or stopping performance of the contract. It only entitles the promisee to the normal remedy for breach of contract, that is, to claim damages to compensate for losses, if any, that flow from the breach. The case of Bettini v Gye illustrates the point.
In view of this, FoodCo is not entitled to return the jars to Ben. FoodCo would not be entitled to recover the purchase price in full, and is unlikely to be granted an order of specific performance. In the circumstances, FoodCo must keep the jars and sue for damages if a breach of warranty has caused any loss.