Draw the zero$-$context graph $G_A^0=(V,E)$ for the reaction system $A=(S,A)$ with

$S=\{1,2,3,4\}$ and $A=\{a,b,c,d\},$ where $a=(\{1\},\{4\},\{3\}),b=(\{2\},\{1\},\{2\}),$

$c=(\{3,4\},\{1\},\{1\}),$ and $d=(\{1,2\},\{3\},\{4\}).$ Then, redraw it if needed, so that edges do not

cross and the components are clearly visible.