Bartosiewicz Clinic uses client$-$visits as its measure of activity. During January, the clinic budgeted for $4,200$ client$-$visits, but its actual level of activity was $4,180$ client$-$visits. The clinic has provided the following data concerning the formulas used in its budgeting and its actual results for January:

Data used in budgeting:

Fixed element per month Variable element per client$-$visit

Revenue $ $0$ $ $36\mathrm{.}20$

Personnel expenses $ $28,200$ $ $12\mathrm{.}20$

Medical supplies $1,1006\mathrm{.}20$

Occupancy expenses $10,1001\mathrm{.}00$

Administrative expenses $7,2000\mathrm{.}30$

Total expenses $ $46,600$ $ $19\mathrm{.}70$

Actual results for January:

Revenue $ $126,350$

Personnel expenses $ $70,120$

Medical supplies $ $21,112$

Occupancy expenses $ $14,110$

Administrative expenses $ $7,870$

The activity variance for net operating income in January would be closest to: