Calculating Cross Sectional Dimensions of Steel Bar Under Compression

[Stacyg]

A steel bar of rectangular cross section 120mm x 60mm is compressed along its longitudinal direction by a force of 1500kN. Do the cross sectional dimensions increase or decrease ? Calculate and write down the resulting dimensions for both sides for both sides of the cross section. Youngs modulus E=200GPa, and Poissons rato of v=0.3

I am not sure what equations to use to do this so I haven't showed any attempts.
Any help would be great.

 

[Hootenanny]

HINT: How is Poisson's ratio related to the transverse and longitudinal strains?