A steel pipe of 300-mm outer diameter is fabricated from 6-mmthick plate by welding along a helix that forms an angle of 25° with a plane perpendicular to the axis of the pipe. Knowing that the maximum allowable normal and shearing stresses in the directions respectively normal and tangential to the weld are s 5 50 MPa and t 5 30 MPa, determine the magnitude P of the largest axial force that can be applied to the pipe.