Indicate whether each of the following is a product cost or a period cost:

3.1. Electricity for lighting a factory building = 3.2. Costs of delivering finished bicycles to dealers = 3.4. Cost of a store detective in a retail establishment = 3.5. Cost of eggs in a bakery = 3.6. Cost of chocolate to a candy manufacturer = 3.7. Salary of injection molding machine operator in a plastics factory = 3.8. Salary of a sewing machine operator in a clothing factory = 3.9. Depreciation of a freezer in an ice cream plant =