Two Charges Q_A = +2 μC and Q_B = -

Two charges Q_A = +2 μC and Q_B = - 6μC are located on the x-axis at x_A= - 1 cm and x_B= +2 cm respectively. Where should a third charge, Q_C = + 3μC, be placed on the positive x-axis so that the potential at the origin is equal to zero?

A) x = 4 cm
B) x = +1 cm
C) x =+2 cm
D) x = 3 cm
E) x = 5 cm