(b) That's right. In this case, B has acted in the belief that A had an import licence which would enable A to supply apples at a price of $2 per kilo. Importantly, B's belief was brought about by what A told him. When he told B that he already had the licence A misrepresented an existing fact. If one party to a contract is misled about an existing fact by the other contracting party, and if it would be against good conscience in the circumstances to permit that other party to rely on the true facts in bringing or defending a legal action, then they will be prevented (estopped) from doing so. The court will instead decide the case as if the mistaken belief was true. This is the ordinary doctrine of estoppel (as distinct from promissory estoppel).
In the present case, A will be estopped from relying on his lack of a licence. His obligations to B will be worked out as if he had the necessary licence. A will therefore be liable in damages for breach of contract if he fails to supply B with the promised fruit.