Two Identical Point Charges Q Are Placed Each Diagonally Opposite

Multiple Choice

Two identical point charges Q are placed each diagonally opposite corners of a square (1.0 m on a side) .The magnitude of the electric field at either of the two unoccupied corners is 19.1 N/C.The absolute value of the charge Q is

A) 1.5 nC.
B) 2.4 nC.
C) 3.2 nC.
D) 4.7 nC.
E) 5.9 nC.