Fill in the missing amounts in each of the following eight case situations. Treat each case independently. (Hint: One way to find the missing amounts would be to prepare a contribution margin income statement for each case, enter the known data, and then compute the missing items.) a. Assume that only one product is being sold in each of the following four case situations: (Negative amounts should be indicated by a minus sign. Enter your contribution margin answers as per unit dollar values. Enter your answers rounded to the nearest whole number.) b. Assume that more than one product is being sold in each of the following four case situations: (Negative amounts should be indicated by a minus sign.)