Provide the steps and reasons, as in Exercise 18, to establish the following logical equivalences.
(a) p ∨ [p ∧ (p ∨ q)] ⇔ p
(b) p ∨ q ∨ (¬p ∧ ¬q ∧ r) ⇔ p ∨ q ∨ r
(c) [(¬p ∨ ¬q) → (p ∧ q ∧ r)] ⇔ p ∧ q