A steel plate of 12-in outer diameter is fabricated from 1/4in thick plate by welding along a helix that forms an angle of 25 degrees with a plane perpendicular to the axis of the pipe, knowing that the max allowable normal and shearing stresses on the directions normal and tangential to the weld are σ=12ksi and τ= 7.2 determine the magnitude p of the largest axial force that can be applied to the pipe.