Dynamics: Planar Kinematics

I am having so much trouble on where to begin with this problem (Crying)

Army AB is rotating with an angular velocity of 10 rad/s and an angular acceleration of 20 rad/s^2, both in the clockwise direction. Determine the angular acceleration of arm BC. θ = 30 degrees.

Please forgive me for my MS paint drawing, I'm desperate right now! Also please note that point C is supposed to be parallel with A.

They ask for angular acceleration but honestly I don't see how BC moves either CW or CCW. It seems to be stuck in a straight line constrained by C.