Identical point charges (+50 C) are placed at the corners of a square with sides of 2.0-m length. How much external energy is required to bring a fifth identical charge from infinity to the geometric center of the square? A charge of +3.0 C is distributed uniformly along the circumference of a circle with a radius of 20 cm. How much external energy is required to bring a charge of 25C from infinity to the center of the circle?