Selling price Variable expenses Contribution margin Per Unit Percent of Sales $ 230 100% 115 50% $ 115 50% The company is currently selling 7,000 units per month. Fixed expenses are $581.000 per month. The marketing manager believes that an $11.000 increase in the monthly advertising budget would result in a 100 unit increase in monthly sales. What should be the overall effect on the company's monthly net operating income of this change? increase of $500 O decrease of $500 O decrease of $11,000 O increase of $11,500