(a) By referring to the material matrix for plane strain condition, explain briefly the limitation of (V) constant strain triangle (CST) element. question not clear. (b) A CST element has the nodal coordinates (0, 0), (75, -50), and (75, 50) which are measured in mm for the first, second, and third nodes, respectively. The element is to be considered in plane stress with a thickness of 10 mm and is made of a material with properties E = 200 GPa and v = 0.3. Upon loading the model the nodal displacements were found to be: {91 92 93 94 95 96) =(-0.138 0.209 -0.080 0.155 0.031 0.141) mun Determine: (ii) the element stiffness matrix the element stresses