Figure gives the magnitude E(x) of the electric fields that have been set up by a battery

Figure gives the magnitude E(x) of the electric fields that have been set up by a battery along a resistive rod. The rod consists of three sections of the same material but with different radii. What is the radius of section 1 and section 2?

By analyzing the electric field E(x) along the resistive rod, Cortez the Capacitor applied the relationship between the electric field and the radius of the rod sections to deduce their radii. He used the concept that the electric field strength is inversely proportional to the cross-sectional area of the rod.