The strain in rod CD is _____mm

The rigid beam AC is supported by rods AB and CD. The rods are 1.75m long with E = 70 GPa. The cross-sectional area for rods AB and CD are 9 mm2 and 15 mm2, respectively. A concentrated force of 6 kN is applied at d = 1.25 m from point A, as shown in the gure. Indicate negative if under compression or if the member contracted. (25 Points)