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