Question 12 (1 point) Which statement best describes differences and similarities among electrostatic force, magnetic force, and gravitational force? All three follow the inverse square law, with electrostatic force and magnetic force needing two poles or charges. Magnetic force and gravitational force follow the inverse square law, with electrostatic force needing two opposite charges. All three require opposite poles or charges, but only gravitational force follows the inverse square law. Electrostatic force and gravitational force have associated fields, but magnetic force does not. Gravitational force is stronger than electrostatic force, and both follow the inverse square law. Show all your work for full credit. State the formulais) used, substitution of values. and the final answer with appropriate unit and direction if necessary. Question 13 (9 points) The point charges A, B, C and D each have the same magnitude charge of 5.5 uC. Two of the charges are positive as shown and two are negative. The corners of the square are 8.0 cm apart. P B -5:5mCO + 5. 5 MC 80cm ssuco 5. Suc D C (a) Find the net electric force on Charge D. State your the final direction relative to the sides of the square. [7 marks) (b) Find the total electric potential at the centre of the square produced by the system of charges. Show your work. (2 marks)