C={r(a),r(e),p(c),q(b),s(a,b),s(d,b),s(e,d)}

C ∪ {q(a)} by rule 2 with X/a,Y/b

C ∪ {p(a)} by rule 1 with X/a

C ∪ {q(d)} by rule 2 with X/d,Y/b

C ∪ {q(e)} by rule 2 with X/e,Y/d

C ∪ {p(e)} by rule 1 with X/e