The drawing shows two crates that are connected by a steel (Young's modulus 2.0 x 10¹¹ N/m²) wire that passes over a pulley. The unstretched length of the wire is 1.5 m, and its cross-sectional area is 1.9 x 10^-5 m². The pulley is frictionless and massless. When the crates are accelerating, determine the change in length of the wire. Ignore the mass of the wire.