Let x0 of type ι be given.
Let x1 of type (ι → ο) → ο be given.
Let x2 of type ι → ι → ο be given.
Let x3 of type ι be given.
Apply unknownprop_9475f9db34348b67db100836248d4844693614e5a951b989e9f5043adf44fcda with
d8d01.. x0 x1 x2 x3,
x0,
x1,
x2,
x3.
Let x4 of type ι → ι → ο be given.
The subproof is completed by applying H0.