Let x0 of type ι be given.
Let x1 of type ι → ι → ι be given.
Let x2 of type ι → ι be given.
Let x3 of type ι → ο be given.
Apply unknownprop_9be8536173b706235166955c9e469deb6842ecfdd57ba27e98cfdddc8af2a9df with
1670d.. x0 x1 x2 x3,
x0,
x1,
x2,
x3.
Let x4 of type ι → ι → ο be given.
The subproof is completed by applying H0.