Which of the following costs may be classified as direct costs of a toy manufacturer? i Plastic used in the manufacture of a toy. li Salary of the factory manager. il Grease and oil used in the factory machines. iv Wages of the machine operators responsible for making the toys. A. li and iv B. i and iv C. i and it D. i and i A fixed cost is a cost which A. varies in total with changes in the level of activity B. varies inversely in total with changes in the level of activity C. remains constant per unit with changes in the level of activity D. remains constant in total with changes in the level of activity