Leist Clinic uses client-visits as its measure of activity. During September, the clinic budgeted for 2,200 client- visits, but its actual level of activity was 2,170 client-visits. The clinic has provided the following data concerning the formulas to be used in its budgeting: Fixed element per month Revenue Personnel expenses $ 26,600 Medical supplies 1,400 Occupancy expenses 7,600 Administrative expenses 5,300 Total expenses $40.900 The occupancy expenses in the flexible budget for September would be closest to: $12,808 $12,880 $13,583 $13,215 Variable element per client-visit $ 50.80 $ 15.60 9.40 2.40 0.10 $ 27.50