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_8, if x_8 were a doctor, then x_8 is listening to a song. For all x_8, if x_8 listens to a song, then x_8 is a doctor. John is listening to a song.
There is at least one x for which x will listen to a song can be inferred via the existential generalization rule. For all x_8, x_8 is a doctor if and only if x_8 will listen to a song can be inferred via the universal biconditional introduction rule. For all x_8, x_8 will listen to a song if and only if x_8 is a doctor can be inferred via the universal biconditional introduction rule.