Consider the following premises. There is at least one x_13 for which x_13 is not a lawyer. For all x_13, if x_13 were happy, then x_13 is a sailor. For all x_13, if x_13 were a sailor, then x_13 is happy. For all x_13, x_13 is happy if and only if x_13 is a lawyer. Can we infer the following from them? There is at least one x_13 for which x_13 is not a sailor.
 From the fact that for all x_13, if x_13 were happy, then x_13 is a sailor, and that for all x_13, if x_13 were a sailor, then x_13 is happy we can infer that for all x_13, x_13 is happy if and only if x_13 is a sailor. From the fact that for all x_13, x_13 is happy if and only if x_13 is a lawyer, and that there is at least one x_13 for which x_13 is not a lawyer we can infer that there is at least one x_13 for which x_13 is not happy. From the fact that for all x_13, x_13 is happy if and only if x_13 is a sailor we can infer that for all x_13, if x_13 were a sailor, then x_13 is happy. Finally, from the fact that for all x_13, if x_13 were a sailor, then x_13 is happy, and that there is at least one x_13 for which x_13 is not happy we can infer that there is at least one x_13 for which x_13 is not a sailor. Therefore, the answer is yes.