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: Susan is writing a letter. If Jennifer cooks, then William is happy. If William were happy, then Susan is not writing a letter. If James works, then Jennifer is cooking.
William is not happy can be inferred via the modus tollens rule. If James works, then William is happy can be inferred via the transitivity rule.