Indicate whether each of the following costs of productive output is usually (a) variable or (b) fixed:

1. Packing materials for stereo components

2. Real estate taxes

3. Gasoline for a delivery truck

4. Property insurance

5. Depreciation expense of buildings (calculated with the straight-line method)

6. Supplies

7. Indirect materials

8. Bottles used to package liquids

9. License fees for company cars

10. Wiring used in radios

11. Machine helper’s wages

12. Wood used in bookcases

13. City operating license

14. Machine depreciation based on machine hours used

15. Machine operator’s hourly wages

16. cost of required outside inspection of each unit produced