An Aluminium alloy (7075-T73) circular hollow tube is under axial compression due to a force P as showed in Figure Q13. The tube has a length L = 3 m, outer diameter D = 42 mm and inner diameter d = 22 mm. Aluminium alloy 7075-T73 has a Young's Modulus E = 72 GPa and yield strength ays = 435 MPa. 0 P L Figure Q13 Assuming the tube to be pinned at both ends, calculate the length of the tube (in meters) below which Euler's formula is no longer valid. Answer to 4 dp. Use pi = 3.14159.