Four point charges are positioned on the rim of a circle. The charge on each of the four is +0.5 µC, +1.5 µC, -1.0 µC, and -0.5 µC. If the electrical potential at the center of the circle due to the +0.5 µC charge alone is 4.5 104 Volt, determine the total electric potential at the center due to the four charges?