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: Thomas is writing a letter or Jennifer is listening to a song. If Mary were rich, then Jennifer is curious. If Jennifer listens to a song, then Mary is rich. Mary is rich if and only if Thomas is writing a letter.
If Jennifer listens to a song, then Jennifer is curious can be inferred via the transitivity rule. If Mary were rich, then Thomas is writing a letter can be inferred via the biconditional elimination rule. If Thomas writes a letter, then Mary is rich can be inferred via the biconditional elimination rule.