Based on the law of contract of the UK. In the scenarios below, which one is an invitation to treat? which one is an offer and which one is a breach of contract?

1. The local Sainsbury's labels its Lamb Steaks with a ticket saying 'Special Offer - 3 for the price of 2'

2. Lilian places a poster on a lamp-post in her street saying 'Please help me find my lost dog Merlin - reward 50'

3. Ahmed calls Simon after seeing an advert for a car for sale asking how many previous owners there have been.

4. George offers to sell his BMW to Fred for 15,000. Fred replied by saying he will buy the BMW for 13,500.

5.George [as above] decides to reply to Fred saying that the BMW is no longer for sale.