4. Confirm your calculations in Requirement 3 above by increasing the unit sales in your worksheet by 20% so that the Data area looks like this: (a) What is net operating income? Note: Negative amount should be indicated by a minus sign. (a) What is net operating income? Note: Negative amount should be indicated by a minus sign. (b) By what percentage did the net operating income increase? 3. Using the degree of operating leverage and without changing anything in your worksheet, calculate the percentage change in net operating income if unit sales increase by 20%