Please help me !! physics , it's killing me, please help!!! Physics!!

A stadium "wave" takes about 11 seconds to complete one cycle around the arena. The radius of the arena is 31 m.

what is the angular speed of the "wave"?

a) 0.57 rad/second
b) 0.83 rad/second
c) 1.1 rad/second


please show me how to set up and solve this stupid problem!! Thank you!!!!!

Angular speed = Angle Moved/Time

Time=11 s Angle= 2pi
Hence here A.S.=2pi/11=0.57