Differential Analysis In each of four independent cases, the amount of differential revenue or dif- ferential cost is as follows (parentheses indicate decreases): 1 2 3 4 Increases (decreases) in: Revenue.. Costs. ..... $18,000 $-0- ($12,000) For each case, determine the missing amount that would be necessary for the net differential amount to be a. $8,000 b. ($4,000) Indicate whether your answers reflect increases or decreases