The accountant for Grove Park Clinic, an outpatient clinic serving primary care needs, has gathered the following monthly expense amounts for two levels of patient activity. 300 Patient Visits 600 Patient Visits Total Cost Total Cost Office supplies $150 $240 Medical assistant's earings $4,200 $5,100 Insurance on building $198 $198 Advertising expense $102 5324 Medical supplies $3,300 $6,600 Physician's earnings $14,040 $14,040 The Office Supplies cost item is a O Mixed cost Variable cost Fixed cost