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: Mary is not playing a game. For all x_12, if x_12 were a poet, then x_12 is playing a game. For all x_12, if x_12 plays a game, then x_12 is a poet.
For all x_12, x_12 is a poet if and only if x_12 will play a game can be inferred via the universal biconditional introduction rule. For all x_12, x_12 will play a game if and only if x_12 is a poet can be inferred via the universal biconditional introduction rule.