What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If Elisabeth listens to a song, then David is writing a letter. David is not writing a letter. For all x_21, x_21 will make tea or x_21 will read a book. Richard is not making tea.
Elisabeth is not listening to a song. David is not writing a letter and Richard is not making tea. Richard is not making tea and David is not writing a letter.