Jackie borrowed $1,000 from Uncle John in 1975, with repayment due in 1977. Jackie never repays the loan, and Uncle John never attempts to collect it. In 2004, Jackie writes Uncle John a letter stating that she is sorry that she did not repay the debt and encloses a check for $100 toward repayment. Uncle John cashes the check. He dies of a heart attack one week later. Uncle John's heirs find the letter and sue Jackie to collect the remaining $900 balance. Analyze the case.