fixed costs may be thought of as the costs of being in business while variable costs are the costs of doing business. in some cases management actions may determine whether a cost is classified as fixed or variable. for example if a truck is rented at a rate per mile the cost is variable. if the truck is purchased and subsequently depreciated by the straight-line method the cost is fixed. the same is true regardless of whether the truck is used in production markrting or administration. marketing and administratin provide many examples of variable and fixed expenses including close counterparts to many of the variable and fixed factory overhead examples listed. for example factory supplies are part of variable factory overhead while office supplies used in sales offices are part of variable marketing expenses.