1. (D • E) ∨ F 2. F → C 3. (D • E) → ∼B 4. (∼B ∨ C) → (A → P) 5. ∼P ∴ ∼A 6. [(~B ∨ C) • A] → P 4, Importation 7. ~[(~B ∨ C) • A] 6,5, Modus Tollens 8. ~(~B ∨ C) ∨ ~A 7, deMorgan's law 9. (~~B • ~C) ∨ ~A 8, deMorgan's law 10. (B • ~C) ∨ ~A 9, Double negation 11. ~A ∨ (B • ~C) 10, commutation 12. |~~A Assumption for Indirect Proof 13. |B • ~C 11,12, Disjunctive syllogism 14 |B 13, Simplification 15. |~C • B 13, Commutation 16. |~C 15, Simplification 17. |~F 2,16 Modus Tollens 18. |F ∨ (D • E) 1, Commutation 19. |D • E 18,17, Disjunctive syllogism 20. |~B 3,19 Modus ponens 21. |B • ~B 14,20 Conjunction 22. ~A lines 12-21 indirect proof Edwin