Consider the following premises. If William were a sailor, then John is playing tennis. If Mary were a server, then Charles is an astronaut. If John plays tennis, then Mary is a server. Can we infer the following from them? If we can, name the inference rule being used: The fact that William were a sailor does not imply that Charles is an astronaut.
 From the fact that if John plays tennis, then Mary is a server, and that if Mary were a server, then Charles is an astronaut we can infer that if John plays tennis, then Charles is an astronaut via transitivity. Finally, from the fact that if William were a sailor, then John is playing tennis, and that if John plays tennis, then Charles is an astronaut we can infer that if William were a sailor, then Charles is an astronaut via transitivity, which contradicts that The fact that William were a sailor does not imply that Charles is an astronaut. Therefore, the answer is no.