Problem: Jane owns a sculpture made by a prominent local artist, and she contracted with Sisko to sell him the sculpture for $4,000. The next day, Jane hears that Sisko is in a bad financial bind and that he probably should not have agreed to spend so much money on a piece of art, even a valuable one. Jane then e-mails Sisko to tell him she will sell him the sculpture for only $2,000 instead. Sisko responds that he will gladly agree to this price reduction. Four hours later, Jane changes her mind and calls Sisko to say that she would rather have the full $4,000 as originally agreed. Sisko insists that he and Jane changed the deal and that he expects to get the sculpture for only $2,000.