In the arrangement shown, the blocks A and B are oscillating horizontally without any relative motion between them. Blocks A and B have masses 2 kg and 1 kg respectively. Spring constant $\mathrm{k}=600\mathrm{N}/\mathrm{m}$. There is no friction between block A and the bottom surface but friction is there between A and B. If amplitude of oscillation is 10 cm, the maximum frictional force acting on B is