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

1. Oil used in manufacturing equipment

2. Hourly wages of inspectors

3. Electricity costs, $0.20 per kilowatt-hour

4. Property insurance premiums, $1,500 per month plus $0.006 for each dollar of property over $2,000,000

5. Janitorial costs, $4,000 per month

6. Pension cost, $0.80 per employee hour on the job

7. Computer chip (purchased from a vendor)

8. Hourly wages of machine operators

9. Straight-line depreciation on the production equipment

10. Metal

11. Packaging

12. Rent on warehouse, $10,000 per month plus $10 per square foot of storage used

13. Plastic

14. Property taxes, $100,000 per year on factory building and equipment

15. Salary of plant manager