decrement in bar

Question

A steel bar of 40 mm x 40mm square cross-section is subjected to an axial compressive load of
200 k N. If the length of the bar is 2 m and E = 200 GPa. The decrement in length of the bar will
be
(a) 1.25 mm                    (b) 2.70 mm
(c) 4.05 mm                    (d) 5.40 mm