2. (12 Points) A parallel-plate capacitor in air has circular plates of 3.90 cm in diameter and a plate separation of 1.5 cm. The capacitor is charged to a 120 V and disconnected from the source. The capacitor is then immersed in a distilled water (k = 80). (a) Find the charge on the capacitor. (b) What is electric field between the plates before the immersion? (c) Find capacitance and potential difference of the capacitor after immersion. (d) What is the change in energy of the capacitor