What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? It is cloudy if and only if Elisabeth is fast. If David writes a letter, then Elisabeth is fast. David is writing a letter if and only if William is a poet. If it is cloudy, then William is a poet.
If it is cloudy, then Elisabeth is fast. If David writes a letter, then William is a poet. If Elisabeth were fast, then it is cloudy. If William were a poet, then David is writing a letter.