<s>[INST] Can you present the derivation of the following logical statement?
((Q ∧ R) → P), (¬(R → S) → (¬W → Q)), (Q ∨ ¬S) ⊢ (R → (P ∨ W)) [/INST] To derive the statement (R → (P ∨ W)) from the premises ((Q ∧ R) → P), (¬(R → S) → (¬W → Q)), and (Q ∨ ¬S), we can use a proof by contradiction. We will assume the opposite of what we are trying to prove (i.e., assume ¬(R → (P ∨ W))), and derive a contradiction.

Here's the derivation:

1. ¬(R → (P ∨ W)) (Assumption)
2. ¬(¬R ∨ (P ∨ W)) (Implication rule, equivalent to R ∧ ¬(P ∨ W))
3. R (Disjunctive syllogism, from 2 and ¬(P ∨ W))
4. ¬(P ∨ W) (From 2 and R)
5. ¬P ∧ ¬W (De Morgan's law, from 4)
6. Q ∨ ¬S (Premise)
7. (Q ∧ R) → P (Premise)
8. ¬(R → S) → (¬W → Q) (Premise)
9. ¬(R → S) (Assumption for a proof by contradiction)
10. ¬¬W → Q (From 8 and 9, by contraposition)
11. W ∨ Q (From 6 and 10, by disjunctive syllogism)
12. P ∨ W (From 7, 3, and modus ponens)
13. P (From 5 and 12, by disjunctive syllogism)
14. P ∨ W (From 13, by addition)
15. ¬P ∧ ¬W (From 5)
16. Contradiction: P ∧ ¬P (From 14 and 15)
17. Therefore, (R → (P ∨ W)) is true by contradiction (from 1).

Thus, we have shown that if ((Q ∧ R) → P), (¬(R → S) → (¬W → Q)), and (Q ∨ ¬S) are true, then (R → (P ∨ W)) must also be true. </s><s>[INST] b) Use the resolution method of propositional logic to show that
the following set of clauses is unsatisfiable:
{{C, ¬C, A}, {C, ¬A}, {¬B, ¬A}, {¬B, C}, {¬C}, {A, B}} [/INST] To show that the set of clauses {{C, ¬C, A}, {C, ¬A}, {¬B, ¬A}, {¬B, C}, {¬C}, {A, B}} is unsatisfiable, we can use the resolution method.

First, we write out all possible pairs of clauses:

From {C, ¬C, A} and {C, ¬A}: We can resolve on C to obtain {¬A, A}, which can be simplified to the empty clause {}.
From {¬B, ¬A} and {¬B, C}: We can resolve on ¬B to obtain {¬A, C}, which can be simplified to {¬A, C}.
From {¬C} and {¬A, C}: We can resolve on C to obtain {¬A}, which can be simplified to {¬A}.
From {A, B} and {¬A}: We can resolve on A to obtain {B}, which cannot be further simplified.
At this point, we have obtained the empty clause {}, which indicates that the set of clauses is unsatisfiable. Therefore, there is no truth assignment that satisfies all the clauses, and the set of clauses is contradictory. </s>