Question 869791
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1.  ~N > (~R > C)
2.  R > N
3.  ~C // N
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4.  (~N & ~R) > C                        1      Exportation
5.  (~N & ~R) > ~(~C)                    4      Double Negation
6.  ~(~N & ~R)                           5,3    Modus Tollens
7.  ~(~N) v ~(~R)                        6      De Morgan's Law
8.  ~(~N) v R                            7      Double Negation
9.  ~N > R                               8      Material Implication
10. ~N > N                               9,2    Hypothetical Syllogism
11. ~(~N) v N                            10     Material Implication
12. N v N                                11     Double Negation
13. N                                    12     Tautology
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