Consider a rectangle with sides of length 5 mm and 7 mm. Three point masses, with electric charge +1 C, -2 uC and +1 C , are placed at the corners, as shown in the diagram below. +1 C y 5 mm -2 +1 C 7 mm (b) Calculate the electric potential a point A. (c) An electron is moved to point A from an infinite distance away. Describe the change in potential energy of the electron.