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 Jessica makes tea, then Thomas is a poet. If Thomas were a poet, then Charles is taking a plane. Jessica is making tea if and only if David is happy.
If Jessica makes tea, then Charles is taking a plane can be inferred via the transitivity rule. If Jessica makes tea, then David is happy can be inferred via the biconditional elimination rule. If David were happy, then Jessica is making tea can be inferred via the biconditional elimination rule.