System is shown in the figure and man is pulling the rope from both sides with constant speed \...

System is shown in the figure and man is pulling the rope from both sides with constant speed \( u \) . Then the speed of the block will be ( \( M \) moves vertical):
(a) \( \frac{3 u}{4} \)
(b) \( \frac{3 u}{2} \)
(c) \( \frac{u}{4} \)
(d) None of these