Charges of +3 µC, -5 µC, q = +7 µC and -2 µC are located at the four corners of a square with side length a = 8 cm . Calculate the electric field at the center of the square. [Hint: Use a coordinate system with North pointing towards the +7 µC charge and East pointing toward the -5 µC charge.]

_________N/C at ______ degrees