How Does Removing a Dielectric Affect Capacitor Energy?

[SoulofLoneWlf]

Homework Statement

An dielectric-filled parallel-plate capacitor has plate area A and plate separation d. The capacitor is connected to a battery that creates a constant voltage V . The dielectric constant is K.

The capactor is now disconnected from the battery, and the dielectric plate is then slowly removed the rest of the way out of the capacitor. Find the new energy of the capacitor, U3.

Homework Equations

not sure i think this is my problem`

The Attempt at a Solution

help?
cannot depend on C apparently

 

[G01]

cannot depend on C apparently

The reason the energy changes is because the capacitance changes when the dielectric constant changes.

How does the capacitance depend on the dielectric constant?