1. (O ⊃ C) • (∼S ⊃ ∼D)
2. (E ⊃ D) • (∼E ⊃ ∼C) / O ⊃ S
3. O ⊃ C 1, Simplification
4. (∼E ⊃ ∼C) • (E ⊃ D) 2, Commutation
5. ∼E ⊃ ∼C 4, Simplification
6. ∼∼C ⊃ ∼∼E 5, Transposition
7. C ⊃ E 6, Double Negation
8. O ⊃ E 3,7, Hypothetical Syllogism
9. E ⊃ D 2, Simplification
10. O ⊃ D 8,9, Hypothetical Syllogism
11. (∼S ⊃ ∼D) • (O ⊃ C) 1, Commutation
12. ∼S ⊃ ∼D 11, Simplification
13. ∼∼D ⊃ ∼∼S 12, Transposition
14. D ⊃ S 13, Double Negation
15. O ⊃ S 10,14, Hypothetical Syllogism
Edwin