A +20-NC Point Charge Is Placed at One Corner of a a Square

Multiple Choice

A +2.0-nC point charge is placed at one corner of a square (1.5 m on a side) , and a −3.0-nC charge is placed on a corner diagonally away from the first charge. What is the magnitude of the electric field at either of the two unoccupied corners?

A) 20 N/C
B) 14 N/C
C) 4.0 N/C
D) 12 N/C
E) 8.0 N/C