A chain position over a certain amount of time
Explanation:
The capacitance in two parallel-plate capacitors is:

For air, we have 
For plastic, we have 
Hence:

a) Recall that the potential difference between the plates is the same (
). The electric field is given by:

The potential difference is defined as:

Replacing:

b) The energy is defined as:

So:

Explanation:
Below is an attachment containing the solution
Answer:
The answer is 80 Joules
Explanation:
Electrical energy = Q x V
Energy = 2 x 40
= 80
I just took the test and it was right :D
The correct answer is B.
I hope this helped! :D