19. Consider the plane stress four-node element shown below. Its global node numbers are shown in the figure. The coordinates of the nodes in the global x-y coordinate systems is shown next to each node.

Nodal displacement vector = {q}:r= {"si, vsi, 1152, U52, "ssi "63> "64, fw} = {0, 0, 0.1, 0, 0.1, 0.1, 0, 0}.

(a) Determine the displacement at the point (x, y) = (0.75, 0.75) by interpolating the nodal displacements.

(b) Compute the Jacobian matrix at the point in (b).

(c) Compute strain ew, at the center of the element.