Let x0 of type ι be given.
Let x1 of type ι → ο be given.
Let x2 of type ι be given.
Assume H1: x1 x2.
Apply Eps_i_ax with
λ x3 . and (prim1 x3 x0) (x1 x3),
x2.
Apply andI with
prim1 x2 x0,
x1 x2 leaving 2 subgoals.
The subproof is completed by applying H0.
The subproof is completed by applying H1.