The revenues needed to earn an operating income of $1,200 can also be calculated directly by recognizing (1)that $3,200 of contribution margin must be earned (fixed costs of $2,000 plus operating income of $1,200) and (2) that each dollar of revenue earns 40 cents of contribution margin. To earn $3,200 of contribution margin, revenues must equal $3,200 t 0.40 = $8,000. The graph in Exhibit 3-2 is very difficult to use if the question is: How many units must Mary sell to earn an operating income of $1,200. Why?