Keeping the Resultant in a Plane

Problem: Two cables pull on the top of a post, A (0, 0, 6) m: AB toward B (3, 2, 0) m with 700 N, and AC toward C (\(x\), \(-3\), 0) m with 600 N, where \(x < 0\). Find \(x\) so that the resultant has no \(y\) component, and the resultant.