Consider the following statements: I. Product diversity creates costing problems because diverse products tend to utilize manufacturing activities in different ways. II. Overhead costs that are not incurred at the unit level create costing problems because such costs do not vary with traditional application bases such as direct labor hours or machine hours. III. Product diversity typically exists when a single product (e.g., a ballpoint pen) is made in different colors. Which of the above statements is (are) true?