Monroe manufacturing produces and sells a product with a price of $100/unit. the following data has been prepared for its estimated upper and lower levels of activity. production category lower limit upper limit units of production 4,000 units 6,000 units direct materials $60,000 $90,000 direct labor $80,000 $120,000 manufacturing overhead: indirect materials $25,000 $37,500 indirect labor $40,000 $50,000 depreciation $20,000 $20,000 selling and admin. expenses: sales salaries $50,000 $65,000 office salaries $30,000 $30,000 advertising $45,000 $45,000 other $15,000 $20,000 totals $365,000 $477,500 the only variable expenses for this company are