Let x0 of type ι be given.
Let x1 of type ι be given.
Let x2 of type ι be given.
Let x3 of type ι be given.
Let x4 of type ι be given.
Let x5 of type ι be given.
Let x6 of type ι be given.
Apply binunionI1 with
SetAdjoin (SetAdjoin (SetAdjoin (SetAdjoin (UPair x0 x1) x2) x3) x4) x5,
Sing x6,
x5.
The subproof is completed by applying unknownprop_d5a2b128c5d90052733eb2b6c0d1971691037e7bc096e6812286444e04f288d6 with x0, x1, x2, x3, x4, x5.