4. A steel plate ABCD of thickness t is subjected to uniform stresses $\sigma_x$ and $\sigma_y$ (see Figure). Calculate the change in:
(a) The length of edge AB.
(b) The length of edge AD.
(c) The length of diagonal BD.
(d) The thickness.
Given: a = 160 mm, b = 200 mm, t = 5 mm, $\sigma_x$ = 120 MPa, $\sigma_y$ = 90 MPa, E = 200 GPa, $\nu$ = 1/3