Which of the following activities should be classified as an internal failure cost?

Internal failure costs are costs associated with defects found before the product reaches the customer. These costs include: Investigation of defects: Identifying and analyzing defects within the development process. Rework: Fixing defects found during internal testing or audits. Scrap: Discarding defective parts or products. Downtime: Halting production or development to address defects. Among the given options, investigating the cause of build defects is an internal failure cost because it pertains to finding and analyzing issues within the software before it is released to customers.
Reference: "Quality Planning and Analysis" by J.M. Juran and F.M. Gryna "Total Quality Management" by Besterfield et al.