23) Stonebraker Corporation has provided the following contribution format income statement. All questions concern situations that are within the relevant range. Sales (9,000 units) Variable expenses Contribution margin Fixed expenses Net operating income Required: $ 270,000 189,000 81,000 77,400 $ 3,600 a. If sales increase to 9,040 units, what would be the estimated increase in net operating income? b. If the variable cost per unit increases by $6, spending on advertising increases by $3,000, and unit sales increase by 19,200 units, what would be the estimated net operating income? c. Estimate how many units must be sold to achieve a target profit of $26,100.