What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Richard is not happy. If it is overcast, then Karen is reading a book. If Richard doesn't write a letter, then Karen is reading a book. For all z, z will write a letter if and only if z is happy.
For all z, if z writes a letter, then z is happy. For all z, if z were happy, then z is writing a letter.