**AMC 10 Mock Exam Question 12**

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 a width of $6$ 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?

$\displaystyle\textbf{(A) } \frac{\pi}{3} \qquad\textbf{(B) } \frac{2\pi}{3} \qquad\textbf{(C) } \pi \qquad\textbf{(D) } \frac{4\pi}{3} \qquad\textbf{(E) } \frac{5\pi}{3}$

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