A uniform rod $KJ$ of weight $w$ shown in the figure rests against a frictionless vertical wall at the point $K$ and a rough horizontal surface at point $J.$ It is given that $w = 10 \; \text{kN}, a = 4 \; \text{m}$ and $b = 3\; \text{m}.$
The minimum coefficient of static friction that is required at the point $J$ to hold the rod in equilibrium is _________. (round off to three decimal places)