An aluminium strut 2 m long has a 20 mm × 50 mm rectangular section. The end bolts make it act as a hinged-ended column for buckling about the axis perpendicular to the 50 mm side (50 mm is then the depth), and as a fixed-ended column for buckling about the axis perpendicular to the 20 mm side (20 mm is then the depth). Find the safe central load (kN) with a factor of safety of 2.5. Take E = 70 GPa.