consider the same cantilevered thin-walled i-beam with web and flange thickness 3 mm, height 10 cm, and width 8 cm. the beam is made of a material with a yield stress of 250 mpa. if the only load on this beam is a tip moment, what is the maximum bending moment (in nm) the beam cross-section can carry (it will lead to yield and plasticity in the entire cross section of the beam)? assume the beam material is elastic - perfectly plastic.