Charge +Q Is Placed at -A, and Charge -2q Is

Charge +q is placed at -a, and charge -2q is placed at 2a along the x axis. A third charge -3q is placed on the x axis so that the force on it is zero. The coordinate of the third charge is

A) -8.1a.
B) -10.58a.
C) 1.2a.
D) 0.58a.
E) 8.1a.