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: Sarah is a musician if and only if it is late. If it is late, then Sarah is a musician. If it is late, then Charles is not a doctor. Charles is a doctor.
It is not late can be inferred via the modus tollens rule. If Sarah were a musician, then it is late can be inferred via the biconditional elimination rule. If it is late, then Sarah is a musician can be inferred via the biconditional elimination rule.