Consider the following Helmholtz free-energy for an anisotropic material: v = c(1 3) + 2 (J 1 2 ln(J)) + 3 (14 1), - (4) where C1, C2, and C3 are material parameters, I = trace (C), J = det(F), and I = N CN, with N being the direction of anisotropy. Copute the first Piola-Kirchhoff stress tensor P. You can write your answer using either the indicial notation (i.e., by writing the component Pi) or the tensor notation (i.e., by directly writing P).