Solve this :

8.  A square plate of mass 10 kg and side 20 m is moving along the groove with the help of two ideal rollers (massless), connected at the corners A and B of the square, as shown in the figure. At a certain moment of time, during motion the corner A is moving with velocity 16 m/s downward. Find the speed of corner D.

(A)   32 m/s                                           (B)  16 m/s
(C)  8 m/s                                               (D)  none