the magnitude of the angular velocity of O4B

Question

   An instantaneous configuration of a four-bar mechanism, whose plane is horizontal, is shown in the figure below. At this instant, the angular velocity and angular acceleration of link Q₂ A are ω = 8 rad/s and α = 0, respectively, and the driving torque (T) is zero. The link Q₂ A is balanced so tht its centre of mass falls at O₂.

 

At the instant considered, what is the magnitude of the angular velocity of O₄B?

      (a) 1 rad/s                                                           (b) 3 rad/s

      (c) 8 rad/s                                                           (d) 64/3 rad/s