Consider the following premises. Jessica is not fast. For all z, if z were a server, then z is fast. If Jessica were not a server, then it is sunny. For all z, if z were fast, then z is a server. Can we infer the following from them? If we can, name the inference rule being used: It is not sunny.
 From the fact that for all z, if z were a server, then z is fast, and that for all z, if z were fast, then z is a server we can infer that for all z, z is a server if and only if z is fast via universal biconditional introduction. From the fact that for all z, z is a server if and only if z is fast we can infer that Jessica is a server if and only if Jessica is fast via universal instantiation. From the fact that Jessica is a server if and only if Jessica is fast, and that Jessica is not fast we can infer that Jessica is not a server via biconditional elimination. Finally, from the fact that if Jessica were not a server, then it is sunny, and that Jessica is not a server we can infer that it is sunny via modus ponens, which contradicts that It is not sunny. Therefore, the answer is no.