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 x_5, if x_5 were a poet, then x_5 is an electrician. For all x_5, x_5 is not an electrician. There is at least one x_5 for which x_5 is a poet if and only if x_5 is happy. For all x_5, if x_5 were an electrician, then x_5 is a poet.
For all x_5, x_5 is not a poet can be inferred via the universal modus tollens rule. For all x_5, x_5 is a poet if and only if x_5 is an electrician can be inferred via the universal biconditional introduction rule. For all x_5, x_5 is an electrician if and only if x_5 is a poet can be inferred via the universal biconditional introduction rule. There is at least one x_5 for which if x_5 were a poet, then x_5 is happy can be inferred via the existential biconditional elimination rule. There is at least one x_5 for which if x_5 were happy, then x_5 is a poet can be inferred via the existential biconditional elimination rule.