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: It is late. Charles is playing squash if and only if Jessica is cooking. Susan is happy. If Charles plays squash, then Susan is not happy.
Charles is not playing squash can be inferred via the modus tollens rule. It is late and Susan is happy can be inferred via the conjunction rule. Susan is happy and it is late can be inferred via the conjunction rule. If Charles plays squash, then Jessica is cooking can be inferred via the biconditional elimination rule. If Jessica cooks, then Charles is playing squash can be inferred via the biconditional elimination rule.