In the figure, two blocks are separated by a uniform strut attached to each block with frictionless pins. Block A weighs 400 N, block B weighs 300 N, and the strut AB weighs 200 N. If μ = 0.25 under block B, determine the minimum coefficient of friction under A to prevent motion. 
For struts or links hinged at both ends:
• Treat them as two-force members.
• Forces always act along the axis of the member.
• Check equilibrium of each block separately.