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: For all x_4, x_4 will not play tennis. Thomas is taking a plane if and only if it is cold. If it is cold, then David is playing tennis.
If Thomas takes a plane, then it is cold can be inferred via the biconditional elimination rule. If it is cold, then Thomas is taking a plane can be inferred via the biconditional elimination rule.