Exercise $4-13$ Missing Data; Basic Cost$-$Volume$-$Profit Concepts $[$LO$1,$ LO$2)$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: