Consider the following premises. For all z, z is a sailor or z will not make tea. For all z, if z were a mechanic, then z is making tea. For all z, if z were a sailor, then z is a mechanic. Can we infer the following from them? If we can, name the inference rule being used: For all z, z will make tea if and only if z is a sailor.
 From the fact that for all z, z is a sailor or z will not make tea we can infer that for all z, if z makes tea, then z is a sailor via universal rewriting. From the fact that for all z, if z were a sailor, then z is a mechanic, and that for all z, if z were a mechanic, then z is making tea we can infer that for all z, if z were a sailor, then z is making tea via universal transitivity. Finally, from the fact that for all z, if z makes tea, then z is a sailor, and that for all z, if z were a sailor, then z is making tea we can infer that for all z, z will make tea if and only if z is a sailor via universal biconditional introduction. Therefore, the answer is yes.