Given premise 3: ∼q
From premise 2 and premise 3, we can infer: (m ∧ n) → p
Given premise 4: s → m
From premise 1 and premise 4, we can infer: r → (s ∧ n)
From step 4 and step 3, we can infer: r → (s ∧ n) → p
Therefore, the conclusion is r → p
Thus, the argument is valid.