Hi, This question is from the SAT OG Book on page 746 # 12.

Note: Figure not drawn to scale

In the figure above, points P, A and B are equally spaced on line L and points P, Q, and R are equally spaced on line M. If PB=4, PR=6, and AQ=4, what is the perimeter of quadrilateral QABR?

I know from the information that PA=AB=2, and that PQ=QR=3. Therefore I know the sides AB=2, AQ=4, QR=3. How do I find BR?

Thanks in advance