Solve the all parts of given problem:

Problem: When a 390 nF air capacitor (1 nF = 10^-9 F) is connected to a power supply, the energy stored in the capacitor is 1.85 x 10^-5 J. While the capacitor is kept connected to the power supply, a slab of dielectric is inserted that completely fills the space between the plates. This increases the stored energy by 2.60 x 10^-5 J.

Part A: What is the potential difference between the capacitor plates?

Part B: What is the dielectric constant of the slab?

I want help to determine the potential difference between the capacitor plates.