Let x0 of type ι be given.
Let x1 of type ι → ι → ι be given.
Let x2 of type ι → ι → ι be given.
Let x3 of type ι → ι be given.
Let x4 of type ι → ι be given.
Apply pack_b_b_u_u_4_eq with
pack_b_b_u_u x0 x1 x2 x3 x4,
x0,
x1,
x2,
x3,
x4.
Let x5 of type ι → ι → ο be given.
The subproof is completed by applying H0.