1. a) Write a derivation to show that {Ax} `KL∃xAx.[You may wish to use an instance of the tautology: ((p → ¬q) →(q → ¬p)).](b) Explain how the deduction theorem can be applied to deducethat {Ax} `KL(Bx → ∃xAx).2. Let Σ be a set of closed wffs and let A, B and C be closedwffs. Recall that for any wff D, (A ∨ D)is an abbreviation for (¬A → D). Suppose that Σ ∪ {(A ∨ (B ∧C))} is consistent. Show that eitherΣ ∪ {A} is consistent or Σ ∪ {B} is consistent.
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