Aparallel-plate capacitor is constructed from two 10 cm

Question

Compute all parts of given question:

Question: A parallel-plate capacitor is constructed from two 10 cm ? 10 cm electrodes spaced 1.0 mm apart. The capacitor plates are charged to ±9 nC, then disconnected from the battery.

Part A: How much energy is stored in the capacitor?

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Part B: Insulating handles are used to pull the capacitor plates apart until the spacing is 2.3 mm. Now how much energy is stored in the capacitor?

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Part C: How much work was done in the process of pulling the plates apart?

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I want help to find how much work was done in the process of pulling the plates apart.