Leftie Corporation has provided the following contribution format income statement. The following information is within the relevant range. Sales (2,000 units) $ 120,000 Variable expenses 90,000 Contribution margin 30,000 Fixed expenses 16,500 Net operating income $ 13,500 Using the degree of operating leverage, the estimated percent increase in net operating income as the result of a 10% increase in sales is closest to: (Round your intermediate calculations to 1 decimal place.)