eliminate h5 with h6 h7
case intro
p q r al_ac betty_beg carl_cac : Prop
h2 : betty_beg → ¬al_ac
h3 : carl_cac → betty_beg
h4 : al_ac
h5 : betty_beg ∨ carl_cac
⊢ False
case intro.inl
p q r al_ac betty_beg carl_cac : Prop
h2 : betty_beg → ¬al_ac
h3 : carl_cac → betty_beg
h4 : al_ac
h6 : betty_beg
⊢ False

case intro.inr
p q r al_ac betty_beg carl_cac : Prop
h2 : betty_beg → ¬al_ac
h3 : carl_cac → betty_beg
h4 : al_ac
h7 : carl_cac
⊢ False