2.7 The following program says that two people are relatives if

(a) one is an ancestor of the other, or

(b) they have a common ancestor, or

(c) they have a common successor: relatives(X, Y) :- ancestor(X, Y). relatives(X, Y) :- ancestor( Y, X). relatives(X, Y) :- % X and Y have a common ancestor ancestor(Z, X), ancestor(Z, Y). relatives(X, Y) :- % X and Y have a common successor ancestor( X, Z), ancestor( Y, Z). Can you shorten this program by using the semicolon notation?