4) An ASTM cast iron (brittle) has minimum ultimate strengths of 210 MPa in tension and 700 MPa in compression. Find the safety factors using the MNS, BCM, and MM theories for each of the following stress states. Plot the failure diagrams in the σ, σ plane to scale and locate the co-ordinates off each stress state A' a) σ =140 MPa; σy = 42 MPa b) σ = 84 MPa, t, =-56 MPa ху c) σ =-42 MPa; σ x d) σx =-70 MPa; t = -35 MPa =-84 MPa, xy = 56 MPa xy