A supplier has contracted to deliver Halloween costumes to a party supply store by October 15th. However, due to a natural disaster near the overseas plant where the costumes are produced, the supplier received the costumes late and could not deliver them until October 20th. The retailer was very concerned about the delay since the costumes will not be sold if they arrive too late and decided to use another supplier who could fill the order by October 18th. Based on the information provided, determine who violated the contract and explain your answer.