Classify the total costs of each of the following as variable, fixed, mixed, or step:
A - Straight line deprectiate on a building
B - Maintenance costs at a hospital
C - Rent on 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 athe number of course sessions varies
F - Lumber used by a house consturction 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