$(7$ marks$)$ Provide a definition for a predicate cousin$($X$,$ Y$)$ with the meaning X is a $($first$)$ cousin of Y$,$ based solely on the parent predicate. Then, use your definition together with the parent clauses below, in order to draw the Prolog execution tree $($showing the substitutions made in each unification and the backtracking steps$)$ for the query:

$?-$ cousin$($ann$,$ X$).$

parent$($pam$,$ bob$).$ parent$($tom$,$ bob$).$ parent$($tom$,$ liz$).$ parent$($bob$,$ ann$).$ parent$($bob$,$ pat$).$ parent$($liz$,$ jim$).$ parent$($liz$,$ evan$).$