The Absolute Potential at the Center of a Square Is

Multiple Choice

The absolute potential at the center of a square is 3. V when a charge of +Q is located at one of the square's corners. What is the absolute potential at the square's center when a second charge of -Q is placed at one of the remaining corners?

A) -6 V
B) -12 V
C) 6 V
D) 12 V
E) zero