Required information [The following information applies to the questions displayed below. 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 income $ 20,000 12,000 8,000 6,000 $ 2,000 13. 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 %