The values of the first three Gauss-Seidel iterations are given for an unknown system. Find the values of the fourth iteration.

$n$	$x_1$	$x_2$	$x_3$
$0$	$0$	$0$	$0$
$1$	3	-4	12
$2$	7	24	-76
$3$	-25	-176	556
$4$