Question

E2 (total) of rod (of length L = 9.15 mm) = 4.18 ×10^3 V/m. E1=1.76 x 10^3. E3=1.57 x 10^3. The rod consists of three sections of the same material but with different radii. The radius of section 3 is 2.27 mm. What is the radius of (a) section 1 and (b) section 2?

If someone could please help???