Proofgold Proof

pf
Let x0 of type ι be given. Assume H0: Union_closed x0. Assume H1: Power_closed x0. Assume H2: Repl_closed x0. Apply and3I with Union_closed x0, Power_closed x0, Repl_closed x0 leaving 3 subgoals. The subproof is completed by applying H0. The subproof is completed by applying H1. The subproof is completed by applying H2. ■