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 Thomas takes a plane, then Jessica is reading a book. Thomas is taking a plane. Jessica is reading a book if and only if David is a lawyer.
Jessica is reading a book can be inferred via the modus ponens rule. If Jessica reads a book, then David is a lawyer can be inferred via the biconditional elimination rule. If David were a lawyer, then Jessica is reading a book can be inferred via the biconditional elimination rule.