Explain whether you regard each of the following costs or categories of costs as fixed, variable, or semivariable with respect to net sales. Briefly explain your reasoning. If you do not believe that a cost fits into any of these classifications, explain.

a. The cost of goods sold.

b. Salaries to salespeople (these salaries include a monthly minimum amount, plus a commission on all sales).

c. Income taxes expense.

d. Property taxes expense.

e. Depreciation expense on a sales showroom, based on the straight-line method of depreciation.

f. Depreciation expense on a sales showroom, based on the double-declining-balance method of depreciation.