What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z, if z makes tea, then z is taking a plane. Richard is taking a plane or Karen is sleeping. For all z, if z takes a plane, then z is making tea. If Karen sleeps, then Richard is making tea.
For all z, z will make tea if and only if z will take a plane. For all z, z will take a plane if and only if z will make tea.