A circular spinner is divided into six regions, as shown. Four regions each have a central angle of x^\circ. The remaining regions have central angles of 20^\circ and 140^\circ. An arrow is attached to the center of the circle. The arrow is spun once. What is the probability that the arrow stops on a shaded region?

**Answer Choices**

A. \frac23

B. \frac78

C. \frac12

D. \frac{5}{12}

E. \frac{7}{12}