Four point charges have the same magnitude of 2.36 10-12 C and are fixed to the corners of a square that is 3.65 cm on a side. Three of the charges are positive and one is negative. Decide the magnitude of the net electric field that exists at the center of the square. I am totally stuck on this I am thinking that i must possibly take .0365m/2 as r and solve it for that way but it doesn’t work out