Education homework help

A -5.00nC point charge is on the axis at x= 1.20 m . A second point charge Q is on the x axis at -0.600m.What must be the sign and magnitude of Q for the resultant electric field at the origin to be 45.0 N/C in the +x direction?What must be the sign and magnitude of Q for the resultant electric field at the origin to be 45.0 N/C in the -X direction?