Following is a list of various costs incurred in producing computer monitors. With respect to the production and sale of these monitors, classify each cost as either variable, fixed, or mixed.

1. Computer chip (purchased from a vendor)

2. Electricity costs, $0.23 per kilowatt-hour

3. Hourly wages of inspectors

4. Hourly wages of machine operators

5. Janitorial costs, $4,000 per month

6. Metal

7. Packaging

8. Pension cost, $0.90 per employee hour on the job

9. Plastic

10. Property insurance premiums, $1,500 per month plus $0.04 for each dollar of property over $1,000,000

11. Property taxes, $375,000 per year on factory building and equipment

12. Oil used in manufacturing equipment

13. Rent on warehouse, $12,800 per month plus $2.50 per square foot of storage used

14. Salary of plant manager

15. Straight-line depreciation on the production equipment