Let x0 of type ι be given.
Let x1 of type ι → ι → ι be given.
Let x2 of type ι → ι be given.
Apply unknownprop_b984a2082829eec635ce65034fa929b4ed4562d9385aff8c07b143a81c537807 with
971d3.. x0 x1 x2,
x0,
x1,
x2.
Let x3 of type ι → ι → ο be given.
The subproof is completed by applying H0.