Let x0 of type ι be given.
Let x1 of type ι be given.
Apply unknownprop_c3fe42b21df0810041479a97b374de73f7754e07c8af1c88386a1e7dc0aad10f with
setminus x0 x1,
x0.
The subproof is completed by applying unknownprop_29bb348fa91dd336b68009f32eb9809a20ab7c7920c130047ad13aae3b335ac5 with x0, x1.