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 Sarah were a sailor, then Mary is a scientist. For all y_2, y_2 is a sailor or y_2 will write a letter. If Sarah writes a letter, then Mary is a scientist. If Mary were a scientist, then Elisabeth is reading a book.
If Sarah were a sailor, then Elisabeth is reading a book can be inferred via the transitivity rule. If Sarah writes a letter, then Elisabeth is reading a book can be inferred via the transitivity rule.