Oslo Company prepared the following contribution format income statement based on a sales volume of 1,000 units (the relevant range of production is 500 units to 1,500 units): Sales Variable expenses: Contribution margin Fixed expenses Net operating incone $ 20,000 12,000 8,000 6,000 $ 2,000 15. Assume that the amounts of the company's total variable expenses and total fixed expenses were reversed. In other words, assume that the total variable expenses are $6,000 and the total fixed expenses are $12,000. Using the degree of operating leverage, what is the estimated percent increase in net operating income of a 5% increase in sales? Increase in net operating income %