The figure below shows an air-filled plate capacitor with plate area A and plate spacing d. An insulator with dielectric constant K fills 1/3 of the plate gap: If d/3 K d. A Determine the effective capacitance of the capacitor C expressed by A, d and K. [Hint: the capacitor can modeled as two series-connected capacitors with plate gaps resp. equal to d/3 and 2d/3] It's one of the following answers: 2K a) 3K +1 EoA 3K b) 2K +3 c) 2K +1 5K d) 4K +1