Selling and administrative expenses are known to be a mixed cost; however, there is a lot of uncertainty about the portion that is fixed. Previous year's experience has provided the following information: Lowest level of sales: 375,000 units Total Operating Expenses: $778,710 Highest level of sales: 750,000 units Total Operating Expenses: $1,026,210 These costs are paid in the month in which they occur. Not included in the above expenses is bad debt expense