Korsak Corporation is a service company that measures its output by the number of customers served. The company has provided the following fixed and variable cost estimates that it uses for budgeting purposes.

Fixed Element per Month Variable Element per Customer Served

Revenue $ $5,500$

Employee salaries and wages $ $43,700$ $ $1,100$

Travel expenses $ $500$

Other expenses $ $43,200$

The planning budget for October was based on serving $23$ customers, but a total of $19$ customers were actually served during October.

The activity variance for net operating income for October would have been closest to: