In the figure below, QR is the arc of a circle with center P. If the length of arc QR is 6pi (i don't know how to do the pi sign, the 3.14 etc), what is the area of sector PQR?

If you can't see the attactment clearly, angle QPR is 30 degrees and the arc opposite of QPR is 6pi. I don't get why the correct answer is 108pi

Thanks a lot!!!!!!!!