What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: For all y, if y were a server, then y is an electrician. For all y, if y were an electrician, then y is a server. There is at least one y for which if y were an electrician, then y is a server.
For all y, y is a server if and only if y is an electrician can be inferred via the universal biconditional introduction rule. For all y, y is an electrician if and only if y is a server can be inferred via the universal biconditional introduction rule. There is at least one y for which y is an electrician if and only if y is a server can be inferred via the existential biconditional introduction rule. There is at least one y for which y is a server if and only if y is an electrician can be inferred via the existential biconditional introduction rule.