(** A last inequality: *)

(* Specifications: *)
Theorem div_mul_le:
forall a b c, b~=0 -> c*(a/b) <= (c*a)/b.
Theorem div_mul_le:
forall a b c, 0<=a -> 0<b -> 0<=c -> c*(a/b) <= (c*a)/b.
Theorem div_mul_le:
forall a b c, 0<=a -> 0<b -> 0<=c -> c*(a/b) <= (c*a)/b.
Theorem quot_mul_le:
forall a b c, 0<=a -> 0<b -> 0<=c -> c*(a÷b) <= (c*a)÷b.