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 curious if and only if Richard is happy. For all y_3, if y_3 takes a plane, then y_3 is happy. For all y_3, if y_3 were happy, then y_3 is taking a plane. For all y_3, y_3 will not take a plane.
If Thomas were curious, then Richard is happy can be inferred via the biconditional elimination rule. If Richard were happy, then Thomas is curious can be inferred via the biconditional elimination rule. For all y_3, y_3 is not happy can be inferred via the universal modus tollens rule. For all y_3, y_3 will take a plane if and only if y_3 is happy can be inferred via the universal biconditional introduction rule. For all y_3, y_3 is happy if and only if y_3 will take a plane can be inferred via the universal biconditional introduction rule.