∀ {M : Type u_1} {X : Type u_2} {Y : Type u_3} [inst : TopologicalSpace M] [inst_1 : TopologicalSpace X]
  [inst_2 : TopologicalSpace Y] [inst_3 : SMul M X] [ContinuousSMul M X] {f : Y → M} {g : Y → X} {b : Y},
  ContinuousAt f b → ContinuousAt g b → ContinuousAt (fun x => f x • g x) b