Required information [The following information applies to the questions displayed below.] Data for Hermann Corporation are shown below: Selling price Variable expenses Contribution margin Per Unit $ 75 Percent of Sales 51 100% 68 $ 24 32% Fixed expenses are $75,000 per month and the company is selling 4,000 units per month. Required: 1-a. How much will net operating income increase (decrease) per month if the monthly advertising budget increases by $9,900, the monthly sales volume increases by 100 units, and the total monthly sales increase by $7,500? 1-b. Should the advertising budget be increased?