Please teach me how to answer this SAT math question.---**Image Description:**
* **Type:** Geometric figure (Circle).
* **Main Elements:**
* A circle with center labeled 'O'.
* Two line segments passing through the center O, labeled as diameters $\overline{PR}$ and $\overline{QS}$.
* Points P, R, Q, S are located on the circumference of the circle.
* The diameters intersect at the center O.
* The points are arranged around the circle in the order P, Q, R, S (implied by the standard notation for arcs and the diagram).
**Textual Information:**
Note: Figure not drawn to scale.
The circle shown has center $O$, circumference $174\pi$, and diameters $\overline{PR}$ and $\overline{QS}$. The length of arc $PS$ is twice the length of arc $PQ$.
What is the length of arc $QR$?
**Options:**
A $58\pi$
B $29\pi$
C $54\pi$