A farmer owns chickens and sheep. One day, he observed that when his animals were all together, there were at least 30 legs but fewer than 12 heads. (All of the animals have the expected number of heads and legs.) Let $\displaystyle{c}\usepackage{cmbright}\Huge\$ be the number of chickens and $\displaystyle{s}\usepackage{cmbright}\Huge\$ be the number of sheep. State a system of inequalities that models this problem and graph it.