When a 360-nF air capacitor (11 nF = 10$^{-9}$ F) is connected to a power supply, the energy stored in the capacitor is 1.85 $\times$ 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 2.32 $\times$ 10$^{-5}$ J. (a) What is the potential difference between the capacitor plates? (b) What is the dielectric constant of the slab?