Let x0 of type ι be given.
Let x1 of type ι → ι be given.
Assume H0: ∀ x2 . x2 ∈ x0 ⟶ x1 x2 ∈ x0.
Let x2 of type ι be given.
Assume H1: x2 ∈ x0.
Let x3 of type ι → ο be given.
Assume H2:
∀ x4 . ∀ x5 : ι → ι . (∀ x6 . x6 ∈ x4 ⟶ x5 x6 ∈ x4) ⟶ ∀ x6 . x6 ∈ x4 ⟶ x3 (pack_u_e x4 x5 x6).
Apply H2 with
x0,
x1,
x2 leaving 2 subgoals.
The subproof is completed by applying H0.
The subproof is completed by applying H1.