Question 3 The following data pertain to STC's operations last year: Sales Net operating income Contribution margin Average operating assets Stockholders' equity Plant, property, & equipment $ 900,000 $ 36,000 $ 150,000 $ 180,000 $ 100,000 $ 120,000 If the residual income for the year was $9,000, the minimum required rate of return must have been: 20% 4% 15% 36%