The accountant for Aspen Park Clinic, an outpatient clinic serving primary care needs, has gathered the following monthly expense amounts for two levels of patient activity. 250 Patient Visits 500 Patient Visits Total Cost Total Cost Office supplies $145 $240 Medical assistant's earings $3,555 $4,360 Insurance on building $95 $95 Advertising expense $145 $290 Medical supplies $2.610 $5.220 Physician's eamings $13,735 $13,735 The Advertising Expense cost item is a Mixed cost Fixed cost Variable cost