7. [-/2 Points] DETAILS OSUNIPHYS1 24.3. WA.020. Three point charges q1, 92, and q3 are situated at three corners of a rectangle as shown in the diagram below. Here q, = +2.00 JC, q2 = -2.00 HC, 93 = +2.80 JC. 2.50 cm 5.00 cm (a) What is the electric potential at the free corner where there is no charge? (b) What charge should be placed at the free corner for the electric potential at the center of the rectangle to be zero? Include the sign of the value in your answer. HC