The resistance in the wire is given by the resistivity of the material by the lenght and divided by the cross-sectional area (R = p*L/A). From here we can rearrange and have p = R*A/L. However, we also know that R = V/I, and thus, our final formula becomes p = V*A / I*L. Plugging in the numbers we get p = 2*3.1*10^-11 / 1.6*0.81, which is equal to 4.78395*10^-11, or rounding, 4.8*10^-11 Ohm-meters.