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_3, x_3 is a poet if and only if x_3 will sleep. There is at least one x_3 for which if x_3 sleeps, then x_3 is not making tea. For all x_3, x_3 will make tea.
There is at least one x_3 for which x_3 will not sleep can be inferred via the existential modus tollens rule. For all x_3, if x_3 were a poet, then x_3 is sleeping can be inferred via the universal biconditional elimination rule. For all x_3, if x_3 sleeps, then x_3 is a poet can be inferred via the universal biconditional elimination rule.