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: David is playing squash if and only if it is sunny. If it is sunny, then Patricia is a taxi driver. If Patricia were a taxi driver, then David is playing squash.
If it is sunny, then David is playing squash can be inferred via the transitivity rule. If David plays squash, then it is sunny can be inferred via the biconditional elimination rule. If it is sunny, then David is playing squash can be inferred via the biconditional elimination rule.