A2/2 (12 marks) The small block at A has a mass of 4 kg and is mounted on an L-shaped rod with negligible mass. If the rotor at B causes a harmonic horizontal motion 8B = 0.1 cos(15t) m, where t is in seconds, determine the steady-state amplitude of vibration of the block (in the vertical direction). 1.2 m A -0.6 m- k = 15 N/m B