Keiko walks once around a track at exactly the same constant speed every day. The sides of the track are straight, and the ends are semicircles. The track has width 6 meters, and it takes her 36 seconds longer to walk around the outside edge of the track than around the inside edge. What is Keiko’s speed in meters per second?

**Answer Choices**

A. \dfrac{\pi}{3}

B. \dfrac{2 \pi}{3}

C. \pi

D. \dfrac{4 \pi}{3}

E. \dfrac{5 \pi}{3}