Consider the following premises. There is at least one x_8 for which x_8 is a cashier if and only if x_8 will make tea. For all x_8, x_8 is a cashier if and only if x_8 is a soldier. Can we infer the following from them? If we can, name the inference rule being used: For all x_8, the fact that x_8 were a soldier does not imply that x_8 is making tea.
 From the fact that there is at least one x_8 for which x_8 is a cashier if and only if x_8 will make tea we can infer that there is at least one x_8 for which if x_8 were a cashier, then x_8 is making tea via existential biconditional elimination. Finally, from the fact that for all x_8, x_8 is a cashier if and only if x_8 is a soldier we can infer that for all x_8, if x_8 were a soldier, then x_8 is a cashier via universal biconditional elimination, which contradicts that For all x_8, the fact that x_8 were a soldier does not imply that x_8 is making tea. Therefore, the answer is no.