$$\text { Reference: } 12 - 10$$ Harstin Corporation Has Provided the Following Data

$$\text { Reference: } 12 - 10$$ Harstin Corporation has provided the following data: $$\begin{array} { | l | r | } \hline \text { Sales } & \$ 625,000 \\\hline \text { Gross margin } & 70,000 \\\hline \text { Net operating income } & 50,000 \\\hline \text { Stockholders' equity } & 90,000 \\\hline \text { Average operating assets } & 250,000 \\\hline \text { Residual income } & 20,000 \\\hline\end{array}$$
-The return on investment for the past year was?

A) 28%.
B) 20%.
C) 8%.
D) 36%.