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 Karen were a police officer, then Thomas is not a cashier. If Richard works, then Thomas is a cashier. Richard is working. Karen is a police officer if and only if William is drinking water.
Thomas is a cashier can be inferred via the modus ponens rule. If Karen were a police officer, then William is drinking water can be inferred via the biconditional elimination rule. If William drinks water, then Karen is a police officer can be inferred via the biconditional elimination rule.