#### Answer

$840N$

#### Work Step by Step

As the bracket is in equilibrium
so $\sum \tau_{pivot}=0$
$\implies F_B\times 4.5-W\times 12=0$
$F_B=\frac{W\times 12}{4.5}=\frac{314\times 12}{4.5}=840N$
We also know that $\sum F_x=0$
$\implies F_{Ax}+F_B=0$
$F_{Ax}=-F_B$
$F_{Ax}=-840N$ The negative sign indicates that the force is in opposite direction.