conv => rhs; rewrite [count_eq_card]
α : Type u
β : Type v
inst✝⁴ : BishopFin α
inst✝³ : BishopFin β
p q : α → Prop
inst✝² : DecidablePred p
inst✝¹ : DecidablePred q
inst✝ : DecidableEq β
f : α → β
⊢ (count fun b => ∃ a, p a ∧ f a = b) ≤ count p
α : Type u
β : Type v
inst✝⁴ : BishopFin α
inst✝³ : BishopFin β
p q : α → Prop
inst✝² : DecidablePred p
inst✝¹ : DecidablePred q
inst✝ : DecidableEq β
f : α → β
⊢ (count fun b => ∃ a, p a ∧ f a = b) ≤ card { a // p a }