William and Charles were business partners. They signed a contract which stated that William would be the publisher of all the books written by Charles, and Charles could get 10% of the listed price multiplied by the number of books sold as royalty.
In 2013, William faced a financial crisis, and Charles, being a good friend of William, agreed to lower the rate of royalty to 5% of the book price. In 2017, William’s financial situation had improved, so Charles sent a notice to William, demanding William to return to him the difference between the original rate and the reduced rate of the royalty he received for five years. Charles also wanted to restore the original rate of royalty. William refused. Comment on the case.