The given contribution format income statement pertains to Sigma Corporation for April 2020. Sales Variable Expenses Contribution Margin Fixed penses Net Operating Income $5,440,000 2,200,000 3,240,000 1,620,000 $1,620,000 The given contribution format income statement pertains to Sigma Corporation for April 2020. Sales Variable Expenses Contribution Margin Fixed penses Net Operating Income $5,440,000 2,200,000 3,240,000 1,620,000 $1,620,000 11. What is the percent change in net operating income that will result from a 15% increase in sales, using the degree of operating leverage? * 7.50% increase O 15% increase O 30% increase O 30% decrease