are the following variable, fixed, mixed, or step?

a. Replacement wheels for toy wagons. b. Wages for sales clerks who are paid for the number of orders they ship. c. Webmaster fee which bills Curtis a base fee plus a small charge for every update made. d. Shipping charges for bulk shipments (billed in 100 pound increments). Telephone charges (base rate plus usage). Rental for warehouse space. Salary for Curtis (president of company). h. Sales bonuses to on-line order clerks of $1 for each clearance item sold. Straight line depreciation on store fixtures. j. Boxes for shipping toys