Peter decides to buy a new business: a newsagency. He goes to see Carmel, the owner of the local newsagency. They swap phone numbers, and tell each other that they will communicate by text to negotiate the sale.

On 5 June 2022, Peter texts Carmel, offering $100,000 to buy her newsagency. On 6 June 2022, she replies stating that she would only sell it for $150,000. Few minutes after this text is sent by Carmel, Peter is rushed to the hospital, as a result of catching COVID-19. He stays in the hospital for 3 days. During his time in hospital, Peter has no access to his phone. When he is discharged from the hospital, he sees Carmel's text mentioned above as well as another text Carmel sent him on 7 June 2022, in which she indicated that she changed her mind and was willing to sell her business to Peter for $100,000. At this point in time, have Peter and Carmel formed a valid agreement for the sale of Carmel's newsagency, according to the law of contract? Please refer to any relevant legal cases and/or legislation to support your arguments.