Classify the total costs of each of the following as variable, fixed, mixed, or step.

a. Straight-line depreciation on a building.

b. Maintenance costs at a hospital.

c. Rent a photocopy machine charged as a fixed amount per month plus an additional charge per copy.

d. Cost of goods sold in a bookstore.

e. Salaries paid to temporary instructors in a college as the number of course sessions varies.

f. Lumber used by a house construction company.

g. The costs of operating a research department.

h. The cost of hiring a dance band for three hours.

i. Laser printer paper for a department printer.

j. Electric power in a restaurant.