(c) Assume that a Prolog database contains the following facts pCa) q(a,l) r(1,1) r(3,5) p(b) qa,2),2) r(3,6) q(b,3) r(2,3) r (4,7) q(b,4) r(2,4) r(4,8) What are the effects of the following queries? 2?- p(X) ,once(q(x,y)),r(Y,z) 3?- p(x), ',q(X, Y)