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 z, z will play tennis if and only if z is fast. If Thomas were fast, then Thomas is playing tennis.
For all z, if z plays tennis, then z is fast can be inferred via the universal biconditional elimination rule. For all z, if z were fast, then z is playing tennis can be inferred via the universal biconditional elimination rule.