Fill in the missing amounts in each of the eight case situations below. Each case is independent of the others. (Hint: One way to find the missing amounts would be to prepare a contribution format income statement for each case, enter the known data, and then compute the missing items.) Required: a. Assume that only one product is being sold in each of the following four case situations: Case #1 Case #2 Case #3 Case #4 Unit sold 15,900 10,600 6.360 Sales 190,800 106,000 $ 318,000 Variable expenses 127,200 74,200 Fixed expenses 53,000 33,920 106,000 Operating income (loss) $ 8,480 $ 12,720 $ (10,600) Contribution margin per unit $ 10 $ 13 b. Assume that more than one product is being sold in each of the following four case situations: (Enter "Contribution margin ratio" in percent. Round your final answers to the nearest whole dollar amount.) Case #1 Case #2 Case #3 Case #4 Sales $ 506,000 $ 406,000 $ 606,000 Variable expenses 263,900 424,200 Fixed expenses 101,500 131,800 Operating income (loss) 7,300 $ 21,800 $ (5,000 Average contribution margin (percentage) 20% 60%