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: If Susan were a cashier, then Elisabeth is bored. For all x_21, x_21 is a poet or x_21 will listen to a song. Elisabeth is not bored. Karen is not a poet.
Susan is not a cashier can be inferred via the modus tollens rule. Elisabeth is not bored and Karen is not a poet can be inferred via the conjunction rule. Karen is not a poet and Elisabeth is not bored can be inferred via the conjunction rule.