Let x0 of type ι be given.
Let x1 of type ι → ι → ι be given.
Assume H0: ∀ x2 . x2 ∈ x0 ⟶ ∀ x3 . x3 ∈ x0 ⟶ x1 x2 x3 ∈ x0.
Let x2 of type ι → ι be given.
Assume H1: ∀ x3 . x3 ∈ x0 ⟶ x2 x3 ∈ x0.
Let x3 of type ι be given.
Assume H2: x3 ∈ x0.
Let x4 of type ι be given.
Assume H3: x4 ∈ x0.
Let x5 of type ι → ο be given.
Assume H4:
∀ x6 . ∀ x7 : ι → ι → ι . (∀ x8 . x8 ∈ x6 ⟶ ∀ x9 . x9 ∈ x6 ⟶ x7 x8 x9 ∈ x6) ⟶ ∀ x8 : ι → ι . (∀ x9 . x9 ∈ x6 ⟶ x8 x9 ∈ x6) ⟶ ∀ x9 . x9 ∈ x6 ⟶ ∀ x10 . x10 ∈ x6 ⟶ x5 (pack_b_u_e_e x6 x7 x8 x9 x10).
Apply H4 with
x0,
x1,
x2,
x3,
x4 leaving 4 subgoals.
The subproof is completed by applying H0.
The subproof is completed by applying H1.
The subproof is completed by applying H2.
The subproof is completed by applying H3.