What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? It is not raining. For all z, z will write a letter if and only if z will cook. It is raining if and only if Richard is cooking.
If it rains, then Richard is cooking. If Richard cooks, then it is raining. Richard is not cooking. For all z, if z writes a letter, then z is cooking. For all z, if z cooks, then z is writing a letter.