Use the rule of interface to show that if A, B, C and D are proposition, the conclusion C or ~D can be interred from the four hypotheses A=>B, B=> ~D, A, and B=>C.
The 'rules' are whether they are Modues ponens, Modus Tollens, Addition, Simplification, Conjuction or Hypothetical syllogism.
My answer -
A=>B, B=> ~D, A, and B=>C.
A, and A ===>B, therefore B
B in turns implies C on one hand and ~D on the other, hence implies C and ~D and
in particular C or ~D.
Is above answer right?