(i) After B reaches the floor, A continues at constant speed until it reaches the pulley (no tension and the surface is smooth). Thus A's speed when B reaches the floor is the same as A's speed (3 m s^-1) when it reaches the pulley. Until the instant when B reached the floor, A and B have the same speed and hence B reaches the floor with speed 3 m s^-1.

(ii) Using energy conservation:

Loss of potential energy (PE) of B is given by:

\(0.15gh\)

Gain of kinetic energy (KE) of the system is:

\(\frac{1}{2} (0.35 + 0.15) \times 3^2\)

Equating loss of PE to gain of KE:

\(0.15gh = \frac{1}{2} \times 0.5 \times 9\)

\(1.5h = 0.25 \times 9\)

\(h = 1.5\)