∀ {M : Type u_1} [inst : TopologicalSpace M] [inst_1 : Mul M] [SeparatelyContinuousMul M] {X : Type u_2}
  [inst_3 : TopologicalSpace X] {f : X → M} {s : Set X} {x : X},
  ContinuousWithinAt f s x → ∀ (b : M), ContinuousWithinAt (fun x => b * f x) s x