Let x0 of type ι be given.
Let x1 of type ι be given.
Let x2 of type (ι → ο) → ο be given.
Let x3 of type ι → ο be given.
Let x4 of type ι be given.
Let x5 of type ι → ο be given.
Assume H1: ∀ x6 . x5 x6 ⟶ x6 ∈ x1.
Apply H0 with
λ x6 x7 . x2 x5 = decode_c (ap x7 1) x5.
Apply tuple_4_1_eq with
x1,
encode_c x1 x2,
Sep x1 x3,
x4,
λ x6 x7 . x2 x5 = decode_c x7 x5.
Let x6 of type ο → ο → ο be given.
Apply decode_encode_c with
x1,
x2,
x5,
λ x7 x8 : ο . x6 x8 x7.
The subproof is completed by applying H1.