What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If Sarah sleeps, then Joseph is an astronaut. Joseph is an astronaut if and only if Elisabeth is happy. Elisabeth is not happy. John is drinking water.
Elisabeth is not happy and John is drinking water. John is drinking water and Elisabeth is not happy. If Joseph were an astronaut, then Elisabeth is happy. If Elisabeth were happy, then Joseph is an astronaut. Joseph is not an astronaut.