James saw a classified advertisement in a magazine offering to sell Kate’s piano for $4000. James wrote to Kate stating that he would "take the instrument at your price". 

On 1st May, Kate wrote to James stating that she now wanted $5,000 and would keep her offer open for a week.

James received the letter on 4th May and wrote back to Kate stating he agreed to pay the $5000 "at your convenience". The letter unfortunately didn't arrive until 11th May.

The next day (5th May), Kate had lunch with her sister Julie. They discussed the piano and agreed that Julie could have the piano for $3,500 if she minded Kate’s children on Saturday nights.

On 6th May, the piano was delivered to Julie's house.