Data for Hermann Corporation are shown below: Selling price Variable expenses Contribution margin Per Unit $ 100 61 $ 39 Percent of Sales 100% 61 39% Fixed expenses are $80,000 per month and the company is selling 3,700 units per month. Required: 1-a. How much will net operating income increase (decrease) per month if the monthly advertising budget increases by $8,500, the monthly sales volume increases by 100 units, and the total monthly sales increase by $10,000? 1-b. Should the advertising budget be increased?