From the stress-strain graph for metallic material, as shown in the adjacent figure. In brief, answer the following questions. a) Up to which region on the stress-strain curve is Hooke's law valid? b) In the elastic region, if we applied a stress of 50000 Pa to produce a strain with 0.5. Calculate the modulus of elasticity. c) Where is the necking region in the stress-strain graph? d) Define the points Y, U, and F shown in the stress-strain graph? e) To which material the stress-strain curve is indicated? Is it ductile or brittle material? justify your answer. Stress, Strain,