Consider the following premises. For all x_12, x_12 is a server if and only if x_12 will write a letter. There is at least one x_12 for which x_12 is a bartender if and only if x_12 is a server. For all x_12, x_12 will not write a letter. For all x_12, if x_12 works, then x_12 is a bartender. Can we infer the following from them? For all x_12, x_12 will work.
 From the fact that for all x_12, x_12 is a server if and only if x_12 will write a letter, and that for all x_12, x_12 will not write a letter we can infer that for all x_12, x_12 is not a server. From the fact that there is at least one x_12 for which x_12 is a bartender if and only if x_12 is a server, and that for all x_12, x_12 is not a server we can infer that there is at least one x_12 for which x_12 is not a bartender. Finally, from the fact that for all x_12, if x_12 works, then x_12 is a bartender, and that there is at least one x_12 for which x_12 is not a bartender we can infer that there is at least one x_12 for which x_12 will not work, which contradicts that For all x_12, x_12 will work. Therefore, the answer is no.