A negative point charge ql = - 4.00 nC is on the x-axis at x = 0.60

Question:

A negative point charge ql = - 4.00 nC is on the x-axis at x = 0.60 m. A second point charge q2 is on the x-axis at x = -1.20 m. What must the sign and magnitude of q2 be for the net electric field at the origin to be?
(a) 50.0 N/C in the + x-direction and
(b) 50.0 N/C in the -x-direction?