Consider the following reduction ad absurdum proof in propositional logic. A combination of derivation lines (to the left, after the line numbers) and justification lines (to the right) are missing. Fill in the blanks.
1. (A v B) ⊃ (C . D) Premise
2. C ⊃ ~ D Premise/ Show ~ A
3. A Assumption for purposes of indirect proof
4. ___ 3, Add
5. C . D 1, 4, MP
6. C 5, Simp
7. ~ D ___
8. D 8, Simp
9. D . ~ D 7, 8, Conj
10. A ⊃ (D . ~ D) 3– 9, Indirect Proof
A v B; 2,6, MP; NC; ~ A
A . B; 2,5 MP; DM, 9,10 MP
A ⊃ B; 2,6 MP; 2 DN; ~ A
A . B; 2,5 MP; NC; 9,10 DN