Can someone please explain the math to me for question one please

Required information Exercise 5-5 Changes in Variable Costs, Fixed Costs, Selling Price, and Volume (LO5-4] (The following information applies to the questions displayed below.) Data for Hermann Corporation are shown below: Percent of Sales 100% 60 Per Unit $ 105 63 Selling price Variable expenses Contribution margin $ 42 40% Fixed expenses are $81,000 per month and the company is selling 3,800 units per month. Exercise 5-5 Part 1 Required: How much will net operating income increase (decrease) per month if the monthly advertising budget increases by $8,600 and monthly sales increase by $18,900? 1-b. Should the advertising budget be increased