Consider the following premises. For all x_21, if x_21 were happy, then x_21 is drinking water. For all x_21, if x_21 were an electrician, then x_21 is a nurse. For all x_21, if x_21 were a janitor, then x_21 is happy. For all x_21, x_21 is an electrician if and only if x_21 will drink water. There is at least one x_21 for which x_21 is a janitor. Can we infer the following from them? For all x_21, x_21 is not a nurse.
 From the fact that for all x_21, x_21 is an electrician if and only if x_21 will drink water we can infer that for all x_21, if x_21 drinks water, then x_21 is an electrician. From the fact that for all x_21, if x_21 were happy, then x_21 is drinking water, and that for all x_21, if x_21 drinks water, then x_21 is an electrician we can infer that for all x_21, if x_21 were happy, then x_21 is an electrician. From the fact that for all x_21, if x_21 were a janitor, then x_21 is happy, and that there is at least one x_21 for which x_21 is a janitor we can infer that there is at least one x_21 for which x_21 is happy. From the fact that for all x_21, if x_21 were happy, then x_21 is an electrician, and that for all x_21, if x_21 were an electrician, then x_21 is a nurse we can infer that for all x_21, if x_21 were happy, then x_21 is a nurse. Finally, from the fact that for all x_21, if x_21 were happy, then x_21 is a nurse, and that there is at least one x_21 for which x_21 is happy we can infer that there is at least one x_21 for which x_21 is a nurse, which contradicts that For all x_21, x_21 is not a nurse. Therefore, the answer is no.