Refer to the process description in E9-7. The following information was pulled from the company's records:

- A container of glass was broken as the result of a forklift accident at the end of the production line.

- Customers returned \(25 \%\) of a shipment to the company because the glass contained impurities.

- The melting oven crew members attended a national glass manufacturers' conference to learn about new manufacturing technologies and methods.

- The company implemented a three-step raw materials inspection program to verify raw material quality and purity.

- Managers at all levels were trained in statistical process control methods.

Classify each event as internal failure, external failure, prevention, or appraisal. Support your answers.