Consider the following premises. For all x_7, x_7 is happy and x_7 is a sailor. For all x_7, x_7 is a lawyer if and only if x_7 is happy. Can we infer the following from them? There is at least one x_7 for which x_7 is not a lawyer.
 From the fact that for all x_7, x_7 is happy and x_7 is a sailor we can infer that for all x_7, x_7 is happy. From the fact that for all x_7, x_7 is a lawyer if and only if x_7 is happy we can infer that for all x_7, if x_7 were happy, then x_7 is a lawyer. Finally, from the fact that for all x_7, if x_7 were happy, then x_7 is a lawyer, and that for all x_7, x_7 is happy we can infer that for all x_7, x_7 is a lawyer, which contradicts that There is at least one x_7 for which x_7 is not a lawyer. Therefore, the answer is no.