Cables A and $B$ act on a bracket as shown. The tension in cable $A$ is $500N,$ oriented as shown. The orientation of $F_B$ is at $=20,$ as shown.

a$.$ Write an expression $($in vector notation$)$ for the resultant force $F_R$ acting on the bracket. Use a coordinate system perpendicular and parallel to the inclined surface.

b$.$ If the bracket will pull away from the wall when the component of $F_R$ parallel to the wall is greater than or equal to $550N$ and the component of $F_R$ perpendicular to the wall is greater than or equal to $600N,$ how large can the magnitude of $F_B$ be$?$