please help me!! I want detail explanation

AP Physics 2 Prep Section II: Free Response the figure shown, four charges are situated at the corners of a square of side tensor ample pages on opposite equal to one another and are labeled O for corners A and C and labeled q for coffers s and D. The charCor. is positive for all experiments. B A + B S X ER Z (out of page) D + 041 > FEA (A) In a first experiment, it is found that the force on the charge at position C is O N. i. Justify the assertion that the charges q cannot have different magnitudes in this experiment. ii. Derive an expression for the magnitude and sign of charge on q in this experiment. (B) In a second experiment, the charge at point C is removed. If the charges q are positive, is there anywhere with- in the boundary square where the electric field could be O N/C? (C) The charges are reassembled into their original positions. In a clear, coherent paragraph-length response, ex- plain why the electric field at the center of the square must be O N/C regardless of the magnitudes of the charges q or Q and regardless of their signs