Which of the following is NOT considered a research and development cost?

Research and development (R&D) costs are typically associated with activities aimed at creating new products or significant improvements to existing products. To determine what is not considered an R&D cost, it is important to understand the nature of the activities involved.

Routine periodic design changes primarily involve enhancing existing products or processes but do not entail significant innovation. These changes are generally aimed at improving efficiency or maintaining the product rather than developing something new. Since R&D focuses on the creation and exploration of new ideas, aspects like routine changes fall outside the scope.

In contrast, activities like quality control testing and developing new products are essential for ensuring a product's feasibility and reliability, which are integral parts of the research and development process. Reformulation of a chemical compound, too, is often part of the R&D cycle, especially when aiming to improve the compound's performance or reduce costs.

Thus, the act of making routine periodic design changes does not fit the definition of R&D costs, as it does not involve the exploration or creation of new products or technologies.