Data for Hermann Corporation are shown below: Selling price Variable expenses Contribution margin Percent of Per Unit $ 95 Sales 57 100% 60 $ 38 40% Fixed expenses are $79,000 per month and the company is selling 3,600 units per month. Required: 1-a. How much will net operating income increase (decrease) per month if the monthly advertising budget increases by $8,400, the monthly sales volume increases by 100 units, and the total monthly sales increase by $9,500? 1-b. Should the advertising budget be increased?