Boston Clinic uses patient-visits as its measure of activity. The clinic has provided the following report:

Boston Clinic
Comparison of planning budget to actual results
For the month ended December 31
	Planing Budget	Actual Reults	Variances
Patiens Visits	2,000	2,400
Revenue ($58.10/ patient)	$116,200	$142,080	$25,880 F
Expenses:
Personnel expenses ($30,000 + $17.40/patient)	65,200	74,250	9,050 U
Medical supplies ($1,300 + $9.6/patient)	20,500	24,670	4,170 U
Occupancy expenses ($9,000 + $1.9/patient)	12,800	14,020	1,220 U
Administrative expenses ($6,200 + $0.30/ patient)	6,800	6,860	60U
Total Expense	105,300	119,800	14,500 U
Net operating income	$10,900	$22,280	$11,380 F

What is the Sales Volume variance of operating income?