Consider the following premises. For all x_8, x_8 is an office clerk if and only if x_8 is a janitor. For all x_8, if x_8 drinks water, then x_8 is an office clerk. For all x_8, if x_8 were a janitor, then x_8 is drinking water. Can we infer the following from them? If we can, name the inference rule being used: There is at least one x_8 for which the fact that x_8 were an office clerk does not imply that x_8 is drinking water.
 From the fact that for all x_8, x_8 is an office clerk if and only if x_8 is a janitor we can infer that for all x_8, if x_8 were an office clerk, then x_8 is a janitor via universal biconditional elimination. From the fact that for all x_8, if x_8 were an office clerk, then x_8 is a janitor, and that for all x_8, if x_8 were a janitor, then x_8 is drinking water we can infer that for all x_8, if x_8 were an office clerk, then x_8 is drinking water via universal transitivity. From the fact that for all x_8, if x_8 drinks water, then x_8 is an office clerk, and that for all x_8, if x_8 were an office clerk, then x_8 is drinking water we can infer that for all x_8, x_8 will drink water if and only if x_8 is an office clerk via universal biconditional introduction. Finally, from the fact that for all x_8, x_8 will drink water if and only if x_8 is an office clerk we can infer that for all x_8, if x_8 were an office clerk, then x_8 is drinking water via universal biconditional elimination, which contradicts that There is at least one x_8 for which the fact that x_8 were an office clerk does not imply that x_8 is drinking water. Therefore, the answer is no.