Could you show me the solution steps for the question below?

A beam of rectangular cross section $($width a$,$depth h$)$is subjected to bending moments M at its ends. The beam is constructed of a material displaying the stress$$strain relationship shown in Figure. What value of M can be carried by the beam? $($Stress$-$Strain Figure is attached$)$

PS: The question doesn't have an illustration or additional explanations; it just asks for the bending moment this beam can carry which I believe is the maximum moment. I added a figure based on what I understood from the question. The topic is related to perfectly plastic beams under simple bending.