Which of the following is an external factor that can change effective capacity?

Machine breakdowns are an internal factor that disrupts production but are not classified as external. While they can significantly affect effective capacity by causing downtime, they stem from issues related to maintenance, operation, or the machinery itself rather than external conditions.

Product mix changes refer to internal decisions regarding which products to manufacture and in what quantities. While they may influence production efficiency and resource allocation, they are not external factors since they result from strategic planning within the organization rather than external influences such as supplier performance or market conditions.

Employee absenteeism is also an internal factor affecting effective capacity. It can reduce workforce availability and productivity, but like machine breakdowns, it arises from internal management and human resource issues rather than external circumstances, making it distinct from external factors like supplier delays.