Let x0 of type ι be given.
Let x1 of type ι be given.
Let x2 of type ι → ι → ι be given.
Let x3 of type ι → ι → ι be given.
Apply unpack_b_o_eq with
λ x4 . λ x5 : ι → ι → ι . explicit_normal x1 x3 x4,
x0,
x2.
Let x4 of type ι → ι → ι be given.
Assume H0: ∀ x5 . x5 ∈ x0 ⟶ ∀ x6 . x6 ∈ x0 ⟶ x2 x5 x6 = x4 x5 x6.
Let x5 of type ο → ο → ο be given.
The subproof is completed by applying H1.