Consider the following premises. Sarah is a server if and only if William is a sailor. Sarah is a server or Charles is listening to a song. If Charles listens to a song, then William is a sailor. Can we infer the following from them? William is a sailor or it is sunny.
 From the fact that Sarah is a server if and only if William is a sailor we can infer that if Sarah were a server, then William is a sailor. From the fact that if Sarah were a server, then William is a sailor, that if Charles listens to a song, then William is a sailor, and that Sarah is a server or Charles is listening to a song we can infer that William is a sailor. Finally, from the fact that William is a sailor we can infer that William is a sailor or it is sunny. Therefore, the answer is yes.