How do I calculate the increase or loss of net operating income?

Per unit Percent of Sales

Selling price $76.00 100%

Variable expenses 41.80 55%

Contribution margin $34.20 45%

Fixed expenses are $75,500 per month and the company is selling 3,200 units per month.

Calculate the increase or decrease in net operating income if a $8,000 increase in the monthly advertising budget would increase monthly sales by $15,000