$(20$pts$)$ Design and instantiate a structure which has $2$ fields: color $($line color$),$ positions

$($positions of a line$).$ color is represented by a string and positions is represented by a list which

has only $2$ elements. Each element is a posn structure with $2$ fields: x $($x coordinate$)$ and y $($y

coordinate$).$ x and y are represented by numbers. $($Do not forget to write down the functions $-$

constructors, selectors, and predicates. Solve Question $2,3$ by using that structure$)$