What is the direction of the net force on q3 where along

Question

Three point charges are arranged along the x-axis. Charge q₁= -4.50 nC is located at x =0.200 m, and charge q₂= +2.50 is at x= -0.300m. A positive point chrge q₃ is located at the origin.

(a) what must the value of q₃ be for the net force on this point charge to have magnitude 4.00 uN?

(b) What is the direction of the net force on q₃?

(c) where along the x axis can q₃ be placed and the net force on the zero, other than the trivial answers of x= +infinity and x= -infinity.