So, I was bothered by the question of natural deduction wherein we have to prove ∀h(Fh ⇒ Fk) from premise ∃g Fg ⇒ Fk given that k is a constant which isn't used before
To get the conclusion in ∀(_) form, we should deduce Fk from Fh. Using existential quantifier premise, we might obtain Fk for variable g but in conclusion the variable altogether is changed (g to h). So, how do we go about proving the conclusion from given premises with the aid of formal proof rules we have like Introduction and Elimination rules?