The following costs and expenses have been taken from income statements of the Firett Company at a representative high and low level of activity. Sales Volume Materials.. Administrative Salaries Office Supplies.. Insurance.. Delivery Expenses. Selling Expenses. Sales Volume of $20,000 of $50,000 $12,000 $30,000 2,000 2,000 100 190 50 50 400 520 200 350 REQUIRED: Using the High Low Points method, compute the cost structure of each expense item in terms of the fixed and variable portions.