$(6)$ The $7-$m uniform bar $AB$ weighs $1\mathrm{.}8$ kN with its center of gravity at $G.$ The bar is supported by a ball$-$and$-$socket joint at $A$ on the floor, and the ball end $B$ rests against the corner of two smooth vertical walls as shown. For the horizontal $1\mathrm{.}6$ kN force applied at $G$ along the $x-$axis direction, determine $($a$)$ the normal forces from the walls at $B($b$)$ the reaction at support $A.$