prolog

Given the following program

road(ottawa,toronto).

road(ottawa,montreal).

road(ottawa,sudbury).

road(toronto,kingston).

road(kingston,ottawa).

road(toronto,windsor).

road(montreal,quebec).

road(calgary,edmonton).

road(edmonton,calgary).

pa(X,Y):- road(X,Y),road(Y,X).

What solutions does the following query produce? Give all solutions in order (found by entering

semi-colons as required).

?- pa(X,Y).