The Excel worksheet form that appears below is to be used to recreate Exhibit 2-9. Download the workbook from Connect, where you will also receive instructions about how to use this worksheet. Required: Check your worksheet by changing the variable selling cost in the Data area to $900, keeping all of the other data the same as in Exhibit 2-9. If your worksheet is operating properly, the net operating income under the traditional formal income statement and under the contribution format income statement should now be $700 and the contribution margin should now be $4, 700. If you do not gel these answers, find the error, in your worksheet and correct them. How much is the gross margin? Did it change? Why or why not? Suppose that sales are 10% higher as shown below: Enter this new data into your worksheet. Make sure that you change all of the data that are different-not just the sales. Print or copy the income statements from your worksheet. What happened to the variable costs and to the fixed costs when sales increased by 10%? Why? Did the contribution margin increase by 10%? Why or why not? Did the net opening income increase by 10%? Why or why not