Graphing The ΔV between three charged metal electrodes

1. The problem statement, all variables and given/known data
Graphing The ΔV between three charged metal electrodes, in regards to x distance

Here is the the picture I'm given with the problem. The hint tells me to assume that V=0 when x=0.

2. Relevant equations
C=Q/ΔV

3. The attempt at a solution
I thought the electrodes looked kinda like a funky capacitor in series, so using Ceq=(1/c1+1/c2) I got ΔV=280 kV across the system. Mastering physics told me this is wrong. I am not sure if even know what equations to use on this one.

The other option maybe to use ΔV=∫Esdx where E=η/ε0
With that ΔV=140 at 1 cm, it then should drop down to zero for 2>x>1, for electric fields can't occur in the middle of a conductor, and ΔV=0 at 3.

We didn't go over this much in class and I'm having trouble finding the relevant parts in my text book.

I solved it:

With that ΔV=140kV at 1 cm, it then should rate of change should be to zero for 2cm>x>1cm so it goes it remains at 140kV, for electric fields can't occur in the middle of a conductor, and it goes to ΔV=0 at 3cm.
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