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: If Susan were a nurse, then it is late. It is late if and only if Elisabeth is reading a book. If Susan were not a nurse, then Elisabeth is sleeping. Elisabeth is not reading a book.
If it is late, then Elisabeth is reading a book can be inferred via the biconditional elimination rule. If Elisabeth reads a book, then it is late can be inferred via the biconditional elimination rule. It is not late can be inferred via the biconditional elimination rule.