Question 1034245
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1. N &#8835; (F • A) 
2. B &#8835; (R • F) / (N &#8744; B) &#8835; (A &#8744; R)

               |3.   N &#8744; B              Assumption for conditional proof 
               |4.  (F • A) &#8744; (R • F)   1,2,3, Constructive dilemma
               |5.  (F • A) &#8744; (F • R)       4, Commutation
               |6.  F • (A &#8744; R)             5, Distribution
               |7.  (A &#8744; R) • F             6, Commutation
               |8.  A &#8744; R                   7, Simplification

9. (N &#8744; B) &#8835; (A &#8744; R)                        3-8 Conditional proof.

Edwin</pre>