A U-shaped wire has a rough semicircular bending between \[A\] and \[B\] as shown in the figure. \[A\] bead of mass m moving with uniform speed \[v\] through the wire enters the semicircular bend at \[A\] and leaves at \[B\] with velocity \[v/2\]after time \[T\]. The average force, exerted by the bead on the part \[A\]\[B\] of the wire is

• A. \[\frac{mv}{2T}\]                     
• B. \[\frac{3mv}{2T}\]
• C. \[\frac{3mv}{T}\]         
• D. None of these