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 $ 20,000 Variable expenses 12,000 Contribution margin 8, 000 Fixed expenses 6,000 Net operating income $ 2,000 13. Using the degree of operating leverage, what is the estimated percent increase in net operating income that would result from a 5% increase in unit sales? Increase in net operating income