(a) That's wrong. A breach of contract, even a serious one, does NOT discharge the contract or make it void. The contract continues to exist and the promises made remain enforceable. The non-defaulting party is entitled to seek a remedy for the breach of contract.
The available remedies include: a claim for damages to compensate for loss suffered as a result of the breach; the right to reject the faulty performance and put a stop to further performance; an order of specific performance; or an injunction to stop a continuing breach. The nature and availability of these remedies is dealt with in the module 'Remedies for breach of contract'.
In the example, the seller has a contractual right to payment, or a claim for damages for the buyer's breach of contract. Because the contract remains in existence despite B's breach it should be noted that A would not be entitled to get the LCD TV and DVD player back from B by claiming that she is still the owner of them. This is because ownership of these things would have passed to the buyer as soon as the contract was made, even though payment is only due later. To avoid this outcome, sellers often include a term in the contract to reserve their ownership in the goods until payment is received. This reserved right of ownership allows the seller to recover the goods as owner if payment is not made, in addition to any action they might have for breach of contract.