Consider the following premises. If Susan were a cashier, then it is late. If it is late, then Susan is a cashier. If Susan were a cashier, then it is late. Can we infer the following from them? If we can, name the inference rule being used: If is not true that it is late if and only if Susan is a cashier.
 From the fact that if Susan were a cashier, then it is late, and that if it is late, then Susan is a cashier we can infer that Susan is a cashier if and only if it is late via biconditional introduction. From the fact that Susan is a cashier if and only if it is late we can infer that if it is late, then Susan is a cashier via biconditional elimination. Finally, from the fact that if it is late, then Susan is a cashier, and that if Susan were a cashier, then it is late we can infer that it is late if and only if Susan is a cashier via biconditional introduction, which contradicts that If is not true that it is late if and only if Susan is a cashier. Therefore, the answer is no.