The image below shows a parallel plate capacitor which has a cross-sectional area A = 10.5 cm2, the distance between the two plates 2d = 7.12 mm. The left half of the capacitor is filled with dielectric material with a dielectric constant K1 = 21 and the right half of the capacitor is filled with two dilectic materials K2 = 42 and K3 = 58.

a. How big is the capacitance of the capacitor?

b. How much energy is stored in the capacitor if the capacitor plates are given a voltage difference of 12 Volts?