(b) That's wrong. But there are limits to the extent to which indirect losses can be claimed. This is because the consequences of a breach of contract can be very far-reaching. If the law made a contracting party liable for every related consequence of a breach, the result would sometimes be unfair and unacceptable. The courts therefore draw a line beyond which there is no liability for losses flowing from the breach.
In addition to direct losses (as illustrated in the previous example) a contracting party is also liable for indirect (or consequential) losses, but only to the extent that it can be inferred from the facts that, when entering the contract, both parties must have had such losses in mind as a probable result of the breach.
In the present case, the facts show that B was clearly informed of the urgency as well as why a quick repair was needed. A would therefore be entitled to claim damages for the lost profits.