∀ {𝕜 : Type u_1} {B : Type u_2} {F : Type u_4} {E : B → Type u_6} [inst : TopologicalSpace B]
  [inst_1 : TopologicalSpace (Bundle.TotalSpace F E)] [inst_2 : (x : B) → TopologicalSpace (E x)]
  [inst_3 : NormedAddCommGroup F] [inst_4 : NontriviallyNormedField 𝕜] [inst_5 : NormedSpace 𝕜 F]
  [inst_6 : FiberBundle F E] [inst_7 : (x : B) → AddCommGroup (E x)] [inst_8 : (x : B) → Module 𝕜 (E x)]
  [VectorBundle 𝕜 F E] {HB : Type u_7} [inst_10 : TopologicalSpace HB] [inst_11 : ChartedSpace HB B] {EB : Type u_8}
  [inst_12 : NormedAddCommGroup EB] [inst_13 : NormedSpace 𝕜 EB] {I : ModelWithCorners 𝕜 EB HB} {s t : (x : B) → E x}
  {u : Set B} {x₀ : B},
  MDifferentiableWithinAt I (I.prod (modelWithCornersSelf 𝕜 F)) (fun x => Bundle.TotalSpace.mk' F x (s x)) u x₀ →
    MDifferentiableWithinAt I (I.prod (modelWithCornersSelf 𝕜 F)) (fun x => Bundle.TotalSpace.mk' F x (t x)) u x₀ →
      MDifferentiableWithinAt I (I.prod (modelWithCornersSelf 𝕜 F)) (fun x => Bundle.TotalSpace.mk' F x ((s - t) x)) u
        x₀