A strut in a steel truss is composed of two equal angles ISA 150 mm × 150 mm of thickness 100 mm connected back-toback to the same side of a gusset plate. The cross sectional area of each angle is 2921 mm² and moment of inertia (I_xx = I_yy) is 6335000 mm⁴ . The distance of the centroid of the angle from its surface (C_x = C_y) is 40.8 mm. The minimum radius of gyration of the sturt is