Fill in the blanks for each of the following independent cases (Click the icon to view the cases.) (For entries with a $0 balance, make sure to enter "O" in the appropriate cell. Round the contribution margin percentage to the nearest whole percent.) Variable Fixed Total Operating Income Case Revenues Contribution Margin Percentage Costs Costs Costs a. $ 800 $ 1.200 % 1,200 $ $ b. S 2,000 $ 400 200 % c. $ 900 $ 500 $ 900 % d. $ 1,800 s 400 50%