Menlo Company distributes a single product. The company's sales and expenses for last month follow: Total Per Unit Sales $ 450,000 $ 30 Variable expenses 180,000 12 Contribution margin 270,000 $ 18 Fixed expenses 216,000 Net operating income $ 54,000 If sales increase by $50,000 per month and there is no change in fixed expenses, by how much would you expect monthly net operating income to increase?