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 it rains, then Michael is writing a letter. Thomas is playing tennis if and only if it is raining. For all y, if y writes a letter, then y is a scientist.
If Thomas plays tennis, then it is raining can be inferred via the biconditional elimination rule. If it rains, then Thomas is playing tennis can be inferred via the biconditional elimination rule.