For each of the following costs, identify the cost behavior as variable, mixed, or fixed:
1. Wages of assembly line workers _________________
2. President’s salary _________________
3. Plant utilities _________________
4. Sales force commissions _________________
5. Shipping costs _________________
6. Factory rent _________________
7. Research and development expenses _________________
8. Property taxes _________________
9. Advertising _________________
10. Supplies used in production _________________