Consider the following premises. It is not late. It is late if and only if Susan is a sailor. Susan is a sailor if and only if it is late. Susan is a sailor or Sarah is a cashier. Can we infer the following from them? Sarah is a cashier.
 From the fact that Susan is a sailor if and only if it is late we can infer that if Susan were a sailor, then it is late. From the fact that it is late if and only if Susan is a sailor we can infer that if it is late, then Susan is a sailor. From the fact that if Susan were a sailor, then it is late, and that if it is late, then Susan is a sailor we can infer that Susan is a sailor if and only if it is late. From the fact that Susan is a sailor if and only if it is late, and that it is not late we can infer that Susan is not a sailor. Finally, from the fact that Susan is a sailor or Sarah is a cashier, and that Susan is not a sailor we can infer that Sarah is a cashier. Therefore, the answer is yes.