What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? It is overcast. If Barbara writes a letter, then Elisabeth is a mechanic. If Joseph were a server, then James is an astronaut. If Elisabeth were a mechanic, then it is not overcast. James is an astronaut if and only if Barbara is writing a letter.
Elisabeth is not a mechanic. If Barbara writes a letter, then it is not overcast. If James were an astronaut, then Barbara is writing a letter. If Barbara writes a letter, then James is an astronaut.