A copper wire has a total lenght of 28m. Half of the wire has a cross-sectional area of 6 mm^2 and the other half of the wire has a cross-sectional area of 4 mm^2 . If the potential difference across the whole wire is 1.0 V, what is the current through this wire? ( The resistivity of copper is 1.72x10^-8 \Omega m)