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 Robert were fast, then it is snowing. If it snows, then Patricia is playing tennis. If Patricia plays tennis, then John is sleeping. If John sleeps, then Patricia is playing tennis.
If Robert were fast, then Patricia is playing tennis can be inferred via the transitivity rule. If it snows, then John is sleeping can be inferred via the transitivity rule. Patricia is playing tennis if and only if John is sleeping can be inferred via the biconditional introduction rule. John is sleeping if and only if Patricia is playing tennis can be inferred via the biconditional introduction rule.