Classification of variable and fixed costs Classify each of the following as a variable or fixed cost with respect to a unit of production:

a. Salaries of production supervisors.

b. Steel used in automobile production.

c. Wood used in furniture production.

d. Salaries for factory custodial staff.

e. Depreciation of factory equipment. f. Lubricants for machines.

g. Electricity used to operate a specific machine.

h. Wages of production workers.

i. Rent for a factory building.

j. Glue used in furniture production.

k. Maintenance for production equipment, performed every month.

l. Paper used in newspaper production.