Consider the following premises. For all x_14, x_14 is a cashier if and only if x_14 will write a letter. Richard is not a cashier. Robert is rich if and only if Richard is writing a letter. For all x_12, x_12 is a janitor if and only if x_12 is rich. Can we infer the following from them? Robert is a janitor.
 From the fact that for all x_14, x_14 is a cashier if and only if x_14 will write a letter we can infer that Richard is a cashier if and only if Richard is writing a letter. From the fact that for all x_12, x_12 is a janitor if and only if x_12 is rich we can infer that Robert is a janitor if and only if Robert is rich. From the fact that Richard is a cashier if and only if Richard is writing a letter, and that Richard is not a cashier we can infer that Richard is not writing a letter. From the fact that Robert is rich if and only if Richard is writing a letter, and that Richard is not writing a letter we can infer that Robert is not rich. Finally, from the fact that Robert is a janitor if and only if Robert is rich, and that Robert is not rich we can infer that Robert is not a janitor, which contradicts that Robert is a janitor. Therefore, the answer is no.