(non-P→Q)→ (non-Q ∪P)=(P ∪Q)→ (non-Q ∪P)

= Fei(P∪Q)∩(Fei Q∪P)=(Fei P∪Fei Q)∩(Fei Q∪P)

= (not P∩ (not Q ∪P)) ∩ (not Q ∪ (not Q∪P))

=T ∩ (not Q∪P)= not Q∪P.