A charge is placed at point O. The electric intensity of point A is 540 NC-. The electric potential of point B is 1.8 x 105 V. The distance between A and B is 40 m and B is between O and A, however is closer to A than it is to O. A point mass (20 mg) containing -4 C on it, is initially at rest at A. Then it starts moving from A towards O due to electromagnetic attraction force. a. Find the value of the charge placed at point O. b. Calculate how much work should be done to bring the -4 C from A to B. c. Calculate the velocity of the -4 C charge at point B.