have h8 : ¬ al_ac := h2 h6
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.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
h8 : ¬al_ac
⊢ False