$(7\mathrm{.}5$: Systems of Inequalities$)$ Graph the given system of inequalities. Tell whether the graph is unbounded or bounded, and Label all points of intersection.

$($a$)x0$

$y0$

$x+y4$

$2x+y>8$

$($b$)x0$

$y0$

$x+y<mn>4</mn>$

$x+3y6.$