廣告應該算係 invitation to treat, bilateral offer 定係 ...?

Advertisements are usually invitations to treat, which allows sellers to refuse to sell products at prices mistakenly marked or avoid some situations that substaantial cosumers go to his shop to buy those products shown on ads.

Advertisements can also be considered unilateral offers in some specific cases.For example, the sellers provide certain discounts on the first ten consumers by posting ads.

But Ads is normally never regarded as a bilateral offer.