For each of the following expenses, select the best allocation basis.
1. Purchasing department expenses for the operating departments.
2. Office department expenses of the operating departments.
3. Advertising expenses of the operating departments.
4. Electric utility expenses of all departments.
a. Relative number of employees.
b. Proportion of total sales for each operating department.
c. Proportion of floor space occupied by each department.
d. Proportion of total purchase orders for each operating department.