
Answer:
There is a decrease in monthly net operating income of $16,000
Explanation:
Consider Incremental Revenues and Costs as a result of the introduction of the  sales commissions.
Sales Commission ( 8,200 units × $11)  ($90,200)
Decrease in Monthly Salary           $74,000
Net Income                        ($16,000)
There is a decrease in monthly net operating income of $16,000