When a 360 -nF air capacitor $\left(1 \mathrm{nF}=10^{-9} \mathrm{F}\right)$ is connected to a power supply, the energy stored in the capacitor is $1.85 \times 10^{-5} \mathrm{J}$ . 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 $2.32 \times 10^{-5} \mathrm{J}$ . (a) What is the potential difference between the capacitor plates? (b) What is the dielectric constant of the slab?