Catherine was walking along the street and saw an advertising poster for fashion coats. She then saw one of the coats in a shop window with a cheap price tag. she really liked that design. She went into the shop took the coat off the stand and took it to the cashier to pay for it. The cashier however refused to sell it to her. He said it was the only one and he needed it for the shop window display. He saw she was upset and said that he would sell her a different style of coat but the same colour for $50. She thought about it and then said she would take it but for $30. He said ok.

With reference to the law of contract rules of offer and acceptance give a legal analysis of the various transactions that occurred in the above story.