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: There is at least one x_10 for which x_10 is an astronaut if and only if x_10 is an electrician. For all x_10, x_10 is an electrician. For all x_10, if x_10 were an astronaut, then x_10 is listening to a song.
There is at least one x_10 for which if x_10 were an astronaut, then x_10 is an electrician can be inferred via the existential biconditional elimination rule. There is at least one x_10 for which if x_10 were an electrician, then x_10 is an astronaut can be inferred via the existential biconditional elimination rule.