1- Decompose the displacement field vector of a 2D 9-nodal isoparametric element. Then write the interpolation of the displacement field at any point (, n) in terms of the node shapes and displacement vector. u (s, n) = {u}} 2- The derivatives of the displacement components are related to the strain vector of the element as follows: (Exx) = Eyy = Iv Iv 3333333 3- The size of the stiffness matrix of the above question is: [ ]