A 0.4 kg bead slides on a curved wire, starting from rest at point A as shown in the figure. The segment from A to B is frictionless, and the segment from B to C is rough. The point A is at height 9 m and the point C is at height 1.8 m with respect to point B. The acceleration of gravity is 9.8 m/s2. Find the speed of the bead at B.