angular velocity of the coupler

Question

The input link Q₂P of a four bar linkage is rotated at 2 rad/s counter clockwise direction as shown below. The angular velocity of the coupler PQ in rad/s, at an instant when ∠O₄O₂P = 180^{0 ,} is      

 

      (a) 2                                (b) 2                      (c) 1                                (d)