Solving a problem in physics section 70 point 5 electr

5. A flat capacitor has between its plates a solid dielectric plate with a permittivity ε = 7, which completely fills the gap between them. The capacitance of the capacitor is equal to C = 100 pF. The capacitor is connected to a source with a voltage of U = 50 V. What work A must be done in order to slowly pull the dielectric plate out of the capacitor? There is no friction.