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: Charles is driving a car if and only if Mary is a bartender. If Sarah were an electrician, then David is a cashier. If Mary were a bartender, then Sarah is an electrician. If David were a cashier, then Charles is driving a car. Charles is not driving a car.
David is not a cashier can be inferred via the modus tollens rule. If Sarah were an electrician, then Charles is driving a car can be inferred via the transitivity rule. If Mary were a bartender, then David is a cashier can be inferred via the transitivity rule. If Charles drives a car, then Mary is a bartender can be inferred via the biconditional elimination rule. If Mary were a bartender, then Charles is driving a car can be inferred via the biconditional elimination rule. Mary is not a bartender can be inferred via the biconditional elimination rule.