The linear density (kg/m) is proportional to the cross-sectional area. The 14 mm diameter bar will have a linear density (14/12)^2 times that of the 12 mm bar.
(14/12)^2*(.89 kg/m) ≈ 1.21 kg/m
(14/12)^2*(.89 kg/m) ≈ 1.21 kg/m
