Question of Law, help!

I have read the answer of Maplesgames. Basically it is alright but I think Fisher v Bell(1961) will be more appropriate as it is displayed in a shop window, rather than in Pharmaceutical Society of GB v Boots Ltd(1953), it was in a self-service shop. Price on the price ticket is not an offer, it is merely an invitation to treat.

Second part of the question is about termination of the offer by revocation (termination by the offeror). An offeror may withdraw an offer at any time before it have been accepted. The revocation must be communicated to the offeree before acceptance but it need not come directly from the offeror. In Dickinson v Dodds (1876), the defendant offered in writing to sell to the plaintiff certain land and stating that the offer would be left over until Friday 9:00am, 12 June 1874. However, the plaintiff was told by a neighbour on 11 June 1874 that the land had been sold to a third party. He then purported to accept the offer. It was held that there was no contract as at the time of acceptance he was aware that the offer has been validly revoked. In answering the question, the reliability of the third party may be worth mentioning.

If good are displayed on the shelves of a department store or supermarket, the store is not offering to sell the goods; it is merely inviting its customers to make an offer to buy them. When the customer takes the goods he has selected to the cash desk, he is offering to but them.

Pharmaceutical Society of Great Britain V Boots Cash Chemists (Southern) Ltd (1953)

所以，間shop擺出黎只係advertisement，就算係話寫錯價錢都冇問題，冇得話佢。但係之後owner講HK$10,000.00就係一個offer勒。而Natalie (N)冇即時accept個offer，所以個contract仲未成立。但係N有 ask for 3 days，所以3days之內如果佢accept都係可以既。Owner其實唔可以隨意賣俾其他人。

An offer may specify that his offer is open for a certain period of time. In the case of Dickinson V Dodds (1876) an offer to sell the property (1st OFFER); an offer to keep the first offer for a period of time (2ND offer).

除非N提出咗其他offer (2nd offer)或owner withdrawing 咗呢個offer before N accept。(Once an offer has been made, the offeror - that is, the person making the offer - may change his mind and decide to withdraw his offer. This process is called revocation of an offer.