Per Percent Unit of Sales $ Selling price 100% 80 Variable $ 65% expenses 52 Contribution $ 35% margin 28 Fixed expenses are $76,000 per month and the company is selling 4,600 units per month. 1. How much will net operating income increase (decrease) per month if the monthly advertising budget increases by $10,000, the monthly sales volume increases by 100 units, and the total monthly sales increase by $8,000? (4