Which of the following is not a valid inference rule in propositional logic?
P ⟹ Q,¬Q⊢¬PP \implies Q, \neg Q \vdash \neg PP⟹Q,¬Q⊢¬P
P∨Q,¬P⊢QP \lor Q, \neg P \vdash QP∨Q,¬P⊢Q
P ⟹ Q,Q⊢PP \implies Q, Q \vdash PP⟹Q,Q⊢P
P ⟹ Q,P⊢QP \implies Q, P \vdash QP⟹Q,P⊢Q