Lister Corporation has provided the following contribution format income statement. Assume that the following information is within the relevant range. Sales (3,000 units) $ 90,000 Variable expenses 58,500 Contribution margin 31,500 Fixed expenses 21,000 Net operating income $ 10,500 If sales increase to 3,040 units, the increase in net operating income would be closest to: (Round your intermediate calculations to 2 decimal places.) a. $420.00 b. $140.00 c. $1,200.00 d. $780.00