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 making tea. William is listening to a song if and only if Mary is making tea. For all x_8, if x_8 listens to a song, then x_8 is a bartender. For all x_8, if x_8 were a bartender, then x_8 is listening to a song.
If William listens to a song, then Mary is making tea can be inferred via the biconditional elimination rule. If Mary makes tea, then William is listening to a song can be inferred via the biconditional elimination rule. William is not listening to a song can be inferred via the biconditional elimination rule. For all x_8, x_8 will listen to a song if and only if x_8 is a bartender can be inferred via the universal biconditional introduction rule. For all x_8, x_8 is a bartender if and only if x_8 will listen to a song can be inferred via the universal biconditional introduction rule.