$1)$ On the $1$st May Arnold offered by email to sell his car to Bertha for $$10,000.$ He also stated that he would send his wife to Bertha$$s house on the $8$th of May to receive Bertha$$s reply. On the $6$th$,$ Bertha sent an email to Arnold saying $$Would like to have the car. Can you offer a six$-$month guarantee against mechanical breakdown?$$ On receiving the email, the same day Arnold sold the car to Cristopher and sent a messenger with a note to Bertha$$s house to tell her of this. Before this note arrived, Bertha changed her mind about the need for guarantee and posted a letter to Arnold accepting the latter$$s offer. This letter was lost in post. Advise Arnold.